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Algebraic Expressions, Identities and Factorisation — MATHS STD 8 — Question

Gujarat BoardEnglish MediumSTD 8MATHSAlgebraic Expressions, Identities and Factorisation1 Mark
MCQ
The value of $(a + b)^2- (a - b)^2$ is:
  • ✓
    $4ab$
  • B
    $-4ab$
  • C
    $2a^2+ 2b^2$
  • D
    $2a^2- 2b^2$
✓

Answer

Correct option: A.
$4ab$
We have,
$ (a+b)^2-(a-b)^2$
$=a^2+b^2+2 a b-\left(a^2+b^2-2 a b\right) $
$ =a^2+b^2+2 a b-a^2-b^2+2 a b$
$=a^2-a^2+b^2-b^2+2 a b+2 a b $
$= 2ab + 2ab$
$= 4ab$

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