If z_1, z_2, z_3 in mathbbC are the vertices of an equilateral triangle, whose centroid is z_0, then sum_k=1^3 (z_k - z_0)^2 is equal to

Solution & Explanation

### Related Formula For any equilateral triangle with vertices z_1, z_2, z_3: z_1^2 + z_2^2 + z_3^2 = z_1 z_2 + z_2 z_3 + z_3 z_1 quad text--- (1) Centroid equation: z_0 = fracz_1 + z_2 + z_33 implies z_1 + z_2 + z_3 = 3z_0 ### Core Logic Let's expand the target sum: sum_k=1^3 (z_k - z_0)^2 = (z_1 - z_0)^2 + (z_2 - z_0)^2 + (z_3 - z_0)^2 ### Step 1: Expansion and Algebraic Grouping Expanding each quadratic term: = (z_1^2 + z_2^2 + z_3^2) - 2z_0(z_1 + z_2 + z_3) + 3z_0^2 Substitute z_1 + z_2 + z_3 = 3z_0: = (z_1^2 + z_2^2 + z_3^2) - 2z_0(3z_0) + 3z_0^2 = z_1^2 + z_2^2 + z_3^2 - 3z_0^2 ### Step 2: Resolving using Equilateral Condition Substitute 3z_0^2 = 3 left(fracz_1+z_2+z_33right)^2 = frac(z_1+z_2+z_3)^23: = (z_1^2 + z_2^2 + z_3^2) - fracz_1^2 + z_2^2 + z_3^2 + 2(z_1z_2 + z_2z_3 + z_3z_1)3 = frac2(z_1^2 + z_2^2 + z_3^2) - 2(z_1z_2 + z_2z_3 + z_3z_1)3 = frac23(z_1^2 + z_2^2 + z_3^2 - (z_1 z_2 + z_2 z_3 + z_3 z_1)) Using condition (1) for equilateral triangles, the terms inside the parentheses equal 0. Thus: = 0 ### Pattern Recognition This is a standard invariant of equilateral triangles. Any translation to center of mass coordinates leaves the shape invariant, making the sum of squares of coordinate vectors relative to the centroid equal to zero. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Mathematics: Complex Numbers

Reference Study Guides

More Complex Numbers Previous-Year Questions — Page 5

Q21 jee_main_2024_29_january_evening Roots of Quadratic Equations
Let alpha, beta be the roots of the equation x^2 - sqrt6 x + 3 = 0 such that operatornameIm(alpha) > operatornameIm(beta). Let a, b be integers not divisible by 3 and n be a natural number such that fracalpha^99beta + alpha^98 = 3^n (a + ib), i = sqrt-1. Then n + a + b is equal to
Numerical Answer. Answer: 49 to 49

Solution

### Related Formula Using Euler's formula: e^itheta = costheta + isintheta ### Core Logic Solving the quadratic root configurations for x^2 - sqrt6x + 3 = 0: x = fracsqrt6 pm sqrt6 - 122 = fracsqrt6 pm isqrt62 = fracsqrt62(1 pm i) Given operatornameIm(alpha) > operatornameIm(beta), we set: alpha = sqrt3 left(frac1+isqrt2right) = sqrt3 e^ipi/4 beta = sqrt3 left(frac1-isqrt2right) = sqrt3 e^-ipi/4 ### Step 1: Simplify Target Expression Let us factor out common variables: fracalpha^99beta + alpha^98 = alpha^98 left( fracalphabeta + 1 right) = fracalpha^98(alpha + beta)beta Since alpha + beta = sqrt6: textValue = frac(sqrt3e^ipi/4)^98 cdot sqrt6sqrt3e^-ipi/4 = 3^49 e^i 98pi/4 cdot sqrt2 e^ipi/4 = 3^49 cdot sqrt2 e^i 99pi/4 Evaluate e^i 99pi/4: 99fracpi4 = 24pi + frac3pi4 implies e^i 99pi/4 = e^i 3pi/4 = frac-1+isqrt2 Substituting this back: textValue = 3^49 cdot sqrt2 left( frac-1+isqrt2 right) = 3^49(-1 + i) ### Step 2: Resolving Constants Comparing with the given expression 3^n(a + ib): n = 49, quad a = -1, quad b = 1 Therefore: n + a + b = 49 - 1 + 1 = 49 ### Pattern Recognition Convert complex expressions into polar form r e^itheta early. Power scaling like alpha^98 becomes simple multiplication under Euler structures. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Mathematics: Complex Numbers and Quadratic Equations
Q29 jee_main_2024_29_january_evening Integral Solutions
Let the set C = left\(x,y)mid x^2 -2^y = 2023, x,yin mathbbNright\. Then sum_(x,y)in C(x + y) is equal to
Numerical Answer. Answer: 46 to 46

Solution

### Related Formula Analyze structural equations through modular constraints (e.g., modulo 3 or 4) to limit potential bounds. ### Core Logic Given the equation: x^2 - 2^y = 2023. Let us inspect the numbers modulo 8: 2023 equiv 7 pmod 8 A perfect square x^2 can only be congruent to 0, 1, 4 pmod 8. * If y geq 3, then 2^y equiv 0 pmod 8 implies x^2 equiv 7 pmod 8, which is impossible. Therefore, y must be less than 3. Since y in mathbbN, the only choices are y = 1 or y = 2. ### Step 1: Testing Small Exponent Valuations * Case 1: y = 1 x^2 - 2^1 = 2023 implies x^2 = 2025 implies x = 45 quad (textsince 45^2 = 2025) This gives a valid natural solution pair: (45, 1). * Case 2: y = 2 x^2 - 2^2 = 2023 implies x^2 = 2027 Since 2027 is not a perfect square, this yields no natural solutions. Thus, the only valid point element inside set C is (45, 1). ### Step 2: Sum Evaluation Evaluating the required target accumulation: sum (x + y) = 45 + 1 = 46 ### Pattern Recognition Exponential Diophantine equations (equations with variables in exponents) are best analyzed using modular arithmetic constraints to quickly find small finite upper bounds. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Mathematics: Principle of Mathematical Induction / Number Theory
Q11 jee_main_2024_27_jan_morning Modulus and Conjugate
If S=\zin C:|z-i|=|z+i|=|z-1|\, then n(S) is:
  • A. 1
  • B. 0
  • C. 3
  • D. 2

Solution

### Related Formula |z - z_1| = |z - z_2| This represents the perpendicular bisector of the line segment joining the points z_1 and z_2 in the complex plane. ### Core Logic The given set defines a complex number z that is equidistant from three fixed points: A equiv (0, 1) corresponding to i B equiv (0, -1) corresponding to -i C equiv (1, 0) corresponding to 1 The condition |z-i|=|z+i|=|z-1| implies that z is the point of intersection of the perpendicular bisectors of the sides of the triangle formed by A, B, and C. ### Step 1: Finding the Circumcenter The point of intersection of the perpendicular bisectors of a triangle is its circumcenter. Since A(0,1), B(0,-1), and C(1,0) form a unique, non-degenerate triangle, they have exactly one unique circumcenter. ### Step 2: Final Conclusion Therefore, there is only one such complex number z that satisfies the condition. n(S) = 1 ### Pattern Recognition Recognize that |z - z_1| = |z - z_2| = |z - z_3| is geometrically identical to finding the circumcenter of a triangle with vertices at z_1, z_2, and z_3. A non-collinear set of three points always yields exactly 1 circumcenter. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Maths: Complex Numbers Class 11 Maths: Straight Lines
Q30 jee_main_2024_27_jan_morning Cube Roots of Unity
If alpha satisfies the equation x^2+x+1=0 and (1+alpha)^7=A+Balpha+Calpha^2, A, B, Cge 0, then 5(3A-2B-C) is equal to:
Numerical Answer. Answer: 5 to 5

Solution

### Related Formula 1 + omega + omega^2 = 0 omega^3 = 1 ### Core Logic The equation x^2 + x + 1 = 0 is the standard identity whose roots are the non-real cube roots of unity, omega and omega^2. Let us assign alpha = omega. We are given the expression (1+alpha)^7. Substituting the root: (1+omega)^7. ### Step 1: Simplify using Unity Properties From the identity 1 + omega + omega^2 = 0, we extract: 1 + omega = -omega^2 Substitute this into the expression: (1+omega)^7 = (-omega^2)^7 = -omega^14 ### Step 2: Cyclical Reduction Using omega^3 = 1, reduce the exponent 14 modulo 3: 14 = 3(4) + 2 Rightarrow omega^14 = (omega^3)^4 cdot omega^2 = 1 cdot omega^2 = omega^2 Thus, the expression reduces to -omega^2. Rewrite this back to its linear form using 1 + omega + omega^2 = 0: -omega^2 = 1 + omega = 1 + alpha ### Step 3: Finding Co-efficients We compare 1 + alpha with A + Balpha + Calpha^2. Notice that 1 + alpha can be directly represented without any alpha^2 term (and we must keep A, B, C ge 0). So, A = 1, B = 1, C = 0. ### Step 4: Final Output Evaluation Substitute these constants into the required equation 5(3A - 2B - C): 5(3(1) - 2(1) - 0) 5(3 - 2) = 5(1) = 5 ### Pattern Recognition The roots of x^2+x+1=0 are always omega, omega^2. Expressions of the form (1+omega)^k rapidly collapse down to single variables via the 1+omega+omega^2=0 rule, making multi-variable polynomial equations instantly trivial. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Maths: Complex Numbers
Q5 jee_main_2024_29_jan_morning Modulus and Equality of Complex Numbers
If z=frac12-2i, is such that |z+1|=alpha z+beta(1+i), i=sqrt-1 and alpha,betain R, then alpha+beta is equal to
  • A. -4
  • B. 3
  • C. 2
  • D. -1

Solution

### Related Formula |x + iy| = sqrtx^2 + y^2 Two complex numbers are equal if and only if their real and imaginary parts are respectively equal. ### Core Logic Given z = frac12 - 2i. Calculate |z + 1|: |z + 1| = left| left(frac12 - 2iright) + 1 right| = left| frac32 - 2i right| = sqrtleft(frac32right)^2 + (-2)^2 = sqrtfrac94 + 4 = sqrtfrac254 = frac52 Now substitute z and |z + 1| into the original equation: frac52 = alphaleft(frac12 - 2iright) + beta(1 + i) Expand and group real and imaginary components on the RHS: frac52 = left(fracalpha2 - 2alpha iright) + (beta + beta i) frac52 = left(fracalpha2 + betaright) + i(beta - 2alpha) ### Step 1: Equate Parts By equating the real and imaginary parts from both sides, we get a system of linear equations: Imaginary part: 0 = beta - 2alpha Rightarrow beta = 2alpha Real part: frac52 = fracalpha2 + beta Substitute beta = 2alpha into the real part equation: frac52 = fracalpha2 + 2alpha frac52 = frac5alpha2 alpha = 1 Using alpha = 1, find beta: beta = 2(1) = 2 ### Step 2: Final Calculation Calculate the final requested value: alpha + beta = 1 + 2 = 3 ### Pattern Recognition Equating complex parts reduces single complex equations into two simultaneous linear equations. Treat |z+1| strictly as a scalar magnitude and parse directly into algebraic components. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Mathematics: Complex Numbers and Quadratic Equations

More Complex Numbers Questions — jee_main_2025_03_april_evening

Practice all Complex Numbers 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%)