Question

simplify 1. (a+3)^3 + (a-3)^3 and 2. (2x-5y)^3 - (2x+5y)^3

Answer 1

Hi ,

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we know the algebraic identity ,

( p + q )³ + ( p - q )³

= p³+3p²q + 3pq² + q³ + p³ - 3p²q + 3pq² - q³

= 2p³ + 6pq²

2 ) ( p - q )³ - ( p + q ) ³

= -2p³ - 6p²q

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Now ,

1 ) ( a + 3 )³ + ( a - 3 )³

= 2a³ + 6 × a × 3²

= 2a³ + 54a

2 ) ( 2x - 5y )³ - ( 2x + 5y )³


= - 2 ( 5y )³ - 2 ×3 ( 2x )² 5y

= - 250y³ - 120x²y

I hope this helps you.

: )