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For any two complex numbers z(1),z(2) th...

For any two complex numbers `z_(1),z_(2)` the values of `|z_(1)+z_(2)|^(2)+|z_(1)-z_(2)|^(2)`, is

A

`|z_(1)|^(2)+|z_(2)|^(2)`

B

`2(|z_(1)|^(2)+|z_(2)|^(2))`

C

`(|z_(1)|+|z_(2)|)^(2)`

D

none of these

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The correct Answer is:
To solve the problem, we need to find the value of \( |z_1 + z_2|^2 + |z_1 - z_2|^2 \) for any two complex numbers \( z_1 \) and \( z_2 \). ### Step-by-step Solution: 1. **Define the Complex Numbers**: Let \( z_1 = a + ib \) and \( z_2 = x + iy \), where \( a, b, x, y \) are real numbers. 2. **Calculate \( |z_1 + z_2|^2 \)**: \[ z_1 + z_2 = (a + x) + i(b + y) \] The modulus squared is: \[ |z_1 + z_2|^2 = (a + x)^2 + (b + y)^2 \] 3. **Calculate \( |z_1 - z_2|^2 \)**: \[ z_1 - z_2 = (a - x) + i(b - y) \] The modulus squared is: \[ |z_1 - z_2|^2 = (a - x)^2 + (b - y)^2 \] 4. **Combine the Two Results**: Now, we need to add these two results: \[ |z_1 + z_2|^2 + |z_1 - z_2|^2 = ((a + x)^2 + (b + y)^2) + ((a - x)^2 + (b - y)^2) \] 5. **Expand the Squares**: Expanding both squares: \[ (a + x)^2 = a^2 + 2ax + x^2 \] \[ (b + y)^2 = b^2 + 2by + y^2 \] \[ (a - x)^2 = a^2 - 2ax + x^2 \] \[ (b - y)^2 = b^2 - 2by + y^2 \] 6. **Combine All Terms**: Now, substituting back: \[ |z_1 + z_2|^2 + |z_1 - z_2|^2 = (a^2 + 2ax + x^2 + b^2 + 2by + y^2) + (a^2 - 2ax + x^2 + b^2 - 2by + y^2) \] Combine like terms: \[ = 2a^2 + 2b^2 + 2x^2 + 2y^2 \] 7. **Factor Out the Common Factor**: \[ = 2(a^2 + b^2 + x^2 + y^2) \] 8. **Relate to Modulus**: Recognizing that: \[ a^2 + b^2 = |z_1|^2 \quad \text{and} \quad x^2 + y^2 = |z_2|^2 \] We can write: \[ = 2(|z_1|^2 + |z_2|^2) \] ### Final Answer: Thus, the value of \( |z_1 + z_2|^2 + |z_1 - z_2|^2 \) is: \[ \boxed{2(|z_1|^2 + |z_2|^2)} \]
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OBJECTIVE RD SHARMA ENGLISH-COMPLEX NUMBERS -Chapter Test
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  2. The locus of the center of a circle which touches the circles |z-z1|=a...

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  3. Prove that for positive integers n(1) and n(2), the value of express...

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  4. The value of abs(sqrt( 2i) - sqrt(2i)) is :

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  5. Prove that the triangle formed by the points 1,(1+i)/(sqrt(2)),a n di ...

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  6. The value of ((1+ i sqrt(3))/(1-isqrt(3)))+ ((1-isqrt(3))/(1+isqrt(3)...

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  7. If alpha+ibeta=tan^(-1) (z), z=x+iy and alpha is constant, the locus o...

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  8. If cosA+cosB+cosC=0,sinA+sinB+sinC=0andA+B+C=180^(@) then the value of...

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  9. Find the sum 1xx(2-omega)xx(2-omega^(2))+2xx(-3-omega)xx(3-omega^(2))+...

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  10. The value of the expression (1+(1)/(omega))+(1+(1)/(omega^(2)))+(2+(1)...

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  11. The condition that x^(n+1)-x^(n)+1 shall be divisible by x^(2)-x+1 is ...

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  12. The expression (1+i)^(n1)+(1+i^(3))^(n2) is real iff

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  13. If |{:(6i,3i,1),(4,3i,-1),(20,3,i):}|=x+iy, then (x, y) is equal to

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  14. If cosalpha+2cosbeta+3cosgamma=sinalpha+2sinbeta+3singamma=0,t h e nt ...

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  15. If cosalpha+2cosbeta+3cosgamma=sinalpha+2sinbeta+3singamma=0,t h e nt ...

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  16. Sum of the series sum(r=0)^n (-1)^r ^nCr[i^(5r)+i^(6r)+i^(7r)+i^(8r)] ...

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  17. If az(1)+bz(2)+cz(3)=0 for complex numbers z(1),z(2),z(3) and real num...

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  18. If 2z1-3z2 + z3=0, then z1, z2 and z3 are represented by

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  19. If Re((z+4)/(2z-1)) = 1/2 then z is represented by a point lying on

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  20. The vertices of a square are z(1),z(2),z(3) and z(4) taken in the anti...

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  21. Let lambda in R . If the origin and the non-real roots of 2z^2+2z+lam...

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