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Simplify (5x − 7y)3 + (5x + 7y)3 - SSC (English Medium) Class 8 - Mathematics

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Question

Simplify

(5x − 7y)+ (5x + 7y)3

Solution

It is known that,

\[\left( a + b \right)^3 = a^3 + b^3 + 3 a^2 b + 3a b^2 ; \left( a - b \right)^3 = a^3 - b^3 - 3 a^2 b + 3a b^2\]

\[\   \left( 5x - 7y \right)^3  +  \left( 5x + 7y \right)^3 \] 

\[ =  \left( 5x \right)^3  -  \left( 7y \right)^3  - 3 \times  \left( 5x \right)^2  \times 7y + 3 \times 5x \times  \left( 7y \right)^2  +  \left( 5x \right)^3  +  \left( 7y \right)^3  + 3 \times  \left( 5x \right)^2  \times \left( 7y \right) + 3 \times 5x \times  \left( 7y \right)^2 \] \[ = 125 x^3  - 343 y^3  - 525 x^2 y + 735x y^2  + 125 x^3  + 343 y^3  + 525 x^2 y + 735x y^2 \] \[ = 250 x^3  + 1470x y^2\]

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APPEARS IN

 Balbharati Solution for Balbharati Class 8 Mathematics (2019 to Current)
Chapter 5: Expansion formulae
Practice set 5.3 | Q: 2.4 | Page no. 27
Solution Simplify (5x − 7y)3 + (5x + 7y)3 Concept: Expansion of (A + B + C)2.
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