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

Solution & Explanation

### 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

Reference Study Guides

More Complex Numbers and Quadratic Equations Previous-Year Questions — Page 7

Q26 jee_main_2024_31_jan_morning Properties of Modulus and Argument
If alpha denotes the number of solutions of |1 - i|^x = 2^x and beta = left(frac|z|arg(z)right), where z = fracpi4 (1 + i)^4 left(frac1 - sqrtpi isqrtpi + i + fracsqrtpi - i1 + sqrtpi iright), i = sqrt-1, then the distance of the point (alpha, beta) from the line 4x - 3y = 7 is
Numerical Answer. Answer: 3 to 3

Solution

### Core Logic |1 - i|^x = 2^x implies (sqrt2)^x = 2^x implies 2^x/2 = 2^x This implies fracx2 = x implies x = 0. There is exactly 1 solution, so alpha = 1. ### Step 1: Simplify complex number z (1+i)^4 = ((1+i)^2)^2 = (1 + i^2 + 2i)^2 = (2i)^2 = -4 Thus, z = -pi left( frac(1-sqrtpii)(sqrtpi-i)pi + 1 + frac(sqrtpi-i)(1-sqrtpii)1 + pi right) ### Step 2: Simplify Bracket Let's expand the terms directly: z = fracpi4(-4) left[ fracsqrtpi - pi i - i - sqrtpipi + 1 + fracsqrtpi - i - pi i - sqrtpi1 + pi right] = -pi left[ frac-i(pi+1)pi+1 + frac-i(pi+1)pi+1 right] = -pi [ -i - i ] = 2pi i ### Step 3: Find beta For z = 2pi i: |z| = 2pi and arg(z) = fracpi2. beta = frac|z|arg(z) = frac2pipi/2 = 4 ### Step 4: Distance from Line Distance of point (alpha, beta) = (1, 4) from the line 4x - 3y - 7 = 0: D = frac|4(1) - 3(4) - 7|sqrt4^2 + (-3)^2 = frac|4 - 12 - 7|5 = frac|-15|5 = 3 ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Maths: Complex Numbers and Quadratic Equations Class 11 Maths: Straight Lines

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