Prove: ${(4 x + 7 y)}^{2} - {(4 x - 7 y)}^{2} = 112 x y$

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Solution

$(4 x + 7 y)^{2} - (4 x - 7 y)^{2}$

we know $(a + b)^{2} - (a - b)^{2} = 4 a b$

$∴ (4 x + 7 y)^{2} - (4 x - 7 y)^{2} = 4.4 x .7 y$

$= 112 x y$

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Similar questions

(4 x + 7 y)^{2} - (4 x - 7 y)^{2}

Coefficient of xy in the expansion of (4x - 7y)² is

3 x^{3} + 2 x^{2} y - 7 x y^{2} + 2 y^{3} - 14 x y + 7 y^{2} + 4 x + 5 y = 0

7 y^{2} + 35 z^{2}

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