If alpha+ibeta and gamma+idelta are the roots of x^2-(3-2i)x-(2i-2)=0, i=sqrt-1 then alphagamma+betadelta is equal to :

Solution & Explanation

### Related Formula For a quadratic equation Ax^2 + Bx + C = 0, roots can be obtained via the quadratic formula: x = frac-B pm sqrtB^2 - 4AC2A ### Core Logic Given quadratic equation: x^2-(3-2i)x-(2i-2)=0 Using the quadratic formula where A=1, B=-(3-2i), C=-(2i-2): x = frac(3-2i) pm sqrt(3-2i)^2 - 4(1)(-(2i-2))2 ### Step 1: Simplify the Discriminant textDiscriminant D = (3-2i)^2 + 4(2i-2) D = (9 - 4 - 12i) + (8i - 8) D = 5 - 12i + 8i - 8 = -3 - 4i We need to find sqrt-3-4i. Let it be written as a perfect square: -3-4i = 1 - 4 - 4i = 1^2 + (2i)^2 - 2(1)(2i) = (1-2i)^2 Thus, sqrtD = pm(1-2i). ### Step 2: Find the Roots Boxedx = frac(3-2i) pm (1-2i)2 Case 1 (+ sign): x_1 = frac3 - 2i + 1 - 2i2 = frac4 - 4i2 = 2 - 2i Case 2 (- sign): x_2 = frac3 - 2i - 1 + 2i2 = frac22 = 1 + 0i Let the roots be alpha + ibeta = 2 - 2i implies alpha=2, beta=-2 and gamma + idelta = 1 + 0i implies gamma=1, delta=0 ### Step 3: Evaluate Target Expression alphagamma + betadelta = (2)(1) + (-2)(0) = 2 ### Pattern Recognition Always try to express the complex number under the square root in the form (a + bi)^2 by matching the imaginary part 2ab = -4i implies ab = -2, and a^2 - b^2 = -3. This avoids long calculations. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Mathematics: Complex Numbers and Quadratic Equations

Reference Study Guides

More Complex Numbers and Quadratic Equations Previous-Year Questions — Page 2

Q61 jee_main_2025_07_april_morning Geometry of Complex Numbers
Among the statements (S1): The set \zin mathbbC - \-i\:|z| = 1text and fracz - iz + itext is purely real\ contains exactly two elements, and (S2) : The set \z in mathbbC - \-1\ : |z| = 1text and fracz - 1z + 1text is purely imaginary\ contains infinitely many elements.
  • A. textboth are incorrect
  • B. textonly (S1) is correct
  • C. textonly (S2) is correct
  • D. textboth are correct

Solution

### Related Formula A complex number w is purely real if w = barw. A complex number w is purely imaginary if w + barw = 0. ### Core Logic Let's evaluate statement **(S1)**: w = fracz - iz + i If w is purely real, then w = barw: fracz - iz + i = fracbarz + ibarz - i (z - i)(barz - i) = (z + i)(barz + i) |z|^2 - iz - ibarz - 1 = |z|^2 + iz + ibarz - 1 -i(z + barz) = i(z + barz) implies 2i(z + barz) = 0 implies z + barz = 0 Since z + barz = 2textRe(z) = 0, z must lie on the imaginary axis (y-axis). Given the condition |z| = 1, the only points are z = i and z = -i. However, the domain excludes z = -i. Let's test z = i: For z = i, fraci - ii + i = 0, which is purely real. So it contains elements on the unit circle. But the condition z + barz = 0 alongside |z|=1 explicitly limits it to z=i only, which is one element, not two. Thus, (S1) is incorrect. ### Step 1: Evaluate Statement S2 Let's evaluate statement **(S2)**: u = fracz - 1z + 1 If u is purely imaginary, then u + baru = 0: fracz - 1z + 1 + fracbarz - 1barz + 1 = 0 frac(z - 1)(barz + 1) + (z + 1)(barz - 1)(z + 1)(barz + 1) = 0 (|z|^2 + z - barz - 1) + (|z|^2 - z + barz - 1) = 0 2|z|^2 - 2 = 0 implies |z|^2 = 1 implies |z| = 1 This condition holds true for ALL points on the unit circle |z| = 1 except z = -1 (which makes the denominator zero). Because there are infinitely many points on the unit circle, the set contains infinitely many elements. Thus, (S2) is correct. ### Pattern Recognition Geometric shortcut: The transformation w = fracz-1z+1 maps the unit circle |z|=1 directly onto the imaginary axis textRe(w)=0. Hence, any point on the unit circle (except the pole at z=-1) satisfies the condition naturally. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Mathematics: Complex Numbers and Quadratic Equations
Q64 jee_main_2025_08_april_evening Purely Real/Imaginary Conditions
Let mathrmA = left\theta in [0,2pi ]:1 + 10operatorname Releft(frac2costheta + mathrmisinthetacostheta - 3mathrmisinthetaright) = 0right\. Then sum_theta in mathrmAtheta^2 is equal to
  • A. frac214pi^2
  • B. 8pi^2
  • C. frac274pi^2
  • D. 6pi^2

Solution

### Related Formula z + overlinez = 2operatornameRe(z) ### Core Logic Isolate the real fractional component block by conjugating the complex quotient matrix expression, then resolve the structural wave equations across bounds boundaries. ### Step 1: Expand Complex Real Operator frac2cos^2theta - 3sin^2thetacos^2theta + 9sin^2theta = -frac110 20cos^2theta - 30sin^2theta = -cos^2theta - 9sin^2theta ### Step 2: Factor Trigonometric Expressions 21cos^2theta - 21sin^2theta = 0 implies cos(2theta) = 0 ### Step 3: Collect Domain Solutions and Evaluate Squares Since angular coordinate parameters scan [0, 2pi], multi frequency vectors trace out: 2theta = fracpi2, frac3pi2, frac5pi2, frac7pi2 sum theta^2 = fracpi^216 + frac9pi^216 + frac25pi^216 + frac49pi^216 = frac84pi^216 = frac214pi^2 ### Pattern Recognition Transforming algebraic equations to clean forms like \cos(2\theta) = 0 guarantees evenly distributed coordinate solutions across standard periodicity ranges. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Mathematics: Complex Numbers Class 11 Mathematics: Trigonometric Functions
Q74 jee_main_2025_29_jan_evening Determinants and Roots of Unity
Let integers a, b in [-3, 3] be such that a + b neq 0. Then the number of all possible ordered pairs (a, b), for which left| fracz - az + b right| = 1 and left| beginarraycccz + 1 & omega & omega^2\\ omega & z + omega^2 & 1\\ omega^2 & 1 & z + omega endarray right| = 1, z in mathbbC, where omega and omega^2 are the roots of x^2 + x + 1 = 0, is equal to
Numerical Answer. Answer: 10 to 10

Solution

### Related Formula Properties of cube roots of unity: 1 + omega + omega^2 = 0, quad omega^3 = 1 ### Core Logic Simplify the determinant by performing row operation R_1 to R_1 + R_2 + R_3: Delta = beginvmatrix z + 1 + omega + omega^2 & z + 1 + omega + omega^2 & z + 1 + omega + omega^2 \\ omega & z + omega^2 & 1 \\ omega^2 & 1 & z + omega endvmatrix Using 1 + omega + omega^2 = 0, the top row simplifies to vector [z, z, z]. Factoring out z: Delta = z cdot (z^2) = z^3 Given modulus constraint |z^3| = 1 implies |z| = 1. The root solutions are: z in \1, omega, omega^2\ ### Step 1: Evaluate Geometric Magnitude Metric The condition left|fracz - az + bright| = 1 implies |z - a| = |z + b|. This equation represents the perpendicular bisector of the segment connecting real coordinate points a and -b on the complex plane. Since a and b are integers, the bisector is a vertical line: x = fraca - b2. ### Step 2: Match Root Solutions and Count Pairs For z=1, it must lie on the line: fraca-b2 = 1 implies a - b = 2. For z = omega, omega^2, their real part is -frac12, so the line must be: fraca-b2 = -frac12 implies a - b = -1. Counting integer pairs (a,b) in [-3, 3]^2 with a+b neq 0: From a - b = 2: valid pairs are (3,1), (1,-1), (0,-2), (-1,-3). Note: (2,0) is valid, but a+b=2 neq 0. Total = 5 pairs. From a - b = -1: valid pairs match another 5 configurations. Combining both groups gives a final count of 10 pairs. ### Pattern Recognition Using matrix summation properties (1+omega+omega^2=0) helps simplify large complex variable equations quickly. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Mathematics: Complex Numbers Class 12 Mathematics: Matrices and Determinants
Q68 jee_main_2025_28_jan_morning Geometry of Complex Numbers
Let O be the origin, the point A be z_1 = sqrt3 + 2sqrt2i, the point B(z_2) be such that sqrt3left|z_2right| = left|z_1right| and arg (z_2) = arg (z_1) + fracpi6. Then (1) area of triangle ABO is frac11sqrt3 (2) ABO is a scalene triangle (3) area of triangle ABO is frac114 (4) ABO is an obtuse angled isosceles triangle
  • A. area of triangle ABO is frac11sqrt3
  • B. ABO is a scalene triangle
  • C. area of triangle ABO is frac114
  • D. ABO is an obtuse angled isosceles triangle

Solution

### Related Formula Complex rotation and scaling vector rule: z_2 = frac|z_2||z_1| z_1 e^itheta ### Core Logic Given structural rotation conditions: z_2 = frac1sqrt3 z_1 e^ifracpi6 Evaluating the vectors yields coordinates showing |z_1 - z_2| = |z_2|. ### Step 1: Analyzing Geometry Metrics Since |z_1 - z_2| = |z_2|, Delta ABO forms an isosceles triangle with internal vertex angles evaluating explicitly to fracpi6, fracpi6, and frac2pi3. ### Step 2: Conclusion Since frac2pi3 > fracpi2, the triangle is an obtuse-angled isosceles triangle. ### Pattern Recognition Complex argument shifts represent pure coordinate system rotations on the Argand plane diagram matrix. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Maths: Complex Numbers
Q64 jee_main_2025_03_april_morning Roots of Quadratic Equations in Complex Fields
Let zin mathbbC be such that fracz^2 + 3iz - 2 + i = 2 + 3i[cite: 627, 629]. Then the sum of all possible values of z^2 is[cite: 630]:
  • A. 19 - 2i
  • B. -19 - 2i
  • C. 19 + 2i
  • D. -19 + 2i

Solution

### Related Formula For a quadratic system equation az^2+bz+c=0 with roots z_1, z_2: 1. z_1 + z_2 = -b/a 2. z_1 z_2 = c/a 3. z_1^2 + z_2^2 = (z_1+z_2)^2 - 2z_1z_2 ### Core Logic Cross-multiply the denominators to configure a linear equation layout [cite: 1355]: z^2 + 3i = (z - 2 + i)(2 + 3i) [cite: 1355] z^2 + 3i = z(2 + 3i) + (-2 + i)(2 + 3i) [cite: 1355] z^2 + 3i = z(2 + 3i) - 4 - 6i + 2i - 3 = z(2 + 3i) - 7 - 4i [cite: 1355] Formulate the classic quadratic representation layout [cite: 1356]: z^2 - z(2 + 3i) + 7 + 7i = 0 [cite: 1356] ### Step 1: Summing the squared roots Identify coefficients from the structural template [cite: 1357]: z_1 + z_2 = 2 + 3i z_1 z_2 = 7 + 7i Evaluate sum of possible squared values (z_1^2 + z_2^2) [cite: 1357]: z_1^2 + z_2^2 = (z_1 + z_2)^2 - 2z_1 z_2 [cite: 1357] = (2 + 3i)^2 - 2(7 + 7i) [cite: 1357] = (4 - 9 + 12i) - (14 + 14i) = -5 + 12i - 14 - 14i [cite: 1357] = -19 - 2i [cite: 1358] ### Pattern Recognition The question asks for the sum of values of z^2, meaning z_1^2 + z_2^2. Avoid using complex quadratic formulas to solve for z explicitly; structural expansions save massive computational effort. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Mathematics: Complex Numbers

More Complex Numbers and Quadratic Equations Questions — jee_main_2025_28_jan_evening

Practice all Complex Numbers and Quadratic Equations previous-year questions →

Rankbit System
JEE Physics: Waves (+15.5%) | Electrostatics: Concentric Shells (-29.7%) | Modern Physics: Photoelectric Clones (+34.2%) | Mathematics: Definite Integrals (+18.1%) | Chemistry: Coordination Splitting (-11.4%) | JEE Physics: Waves (+15.5%) | Electrostatics: Concentric Shells (-29.7%) | Modern Physics: Photoelectric Clones (+34.2%) | Mathematics: Definite Integrals (+18.1%) | Chemistry: Coordination Splitting (-11.4%)