Question

(8)³ - (4)³Evaluate by using the identities.

Answer 1

BONJOUR,
❤ ❤ ❤ ❤ ❤

$8 {}^{3} - 4 {}^{3} \\ a {}^{3} - b {}^{3} = (a - b)(a {}^{2} + b {}^{2} + ab) \\ then \\ 8 {}^{3} - 4 {}^{3} \\ = (8 - 4)(8 {}^{2} + 8 \times 4 + 4 {}^{2} ) \\ 4(64 + 32 + 16) \\ 4 \times 112 \ \\ 448 \\ hope \: it \: helps$

Answer 2

Hi ,

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We know the algebraic identity :

a³ - b³ - 3ab( a - b ) = ( a - b )³

Or

a³ - b³ = ( a - b )³ + 3ab( a - b )
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Here ,

a = 8 , b = 4 ,

8³ - 4³

= ( 8 - 4 )³ + 3 × 8 × 4 ( 8 - 4 )

= 4³ + 3 × 8 × 4 × 4

= 64 + 384

= 448

I hope this helps you.

: )