Question

Find the cube of 21 using a suitable identity

Answer 1

Step-by-step explanation:

21^3 = (20 + 1)^3

= 20^3 + 1^3 + 3×20×1(20×1)

= 8000 + 1 + 60 × 21

= 8000+ 1 + 1260

= 9261

the identity is (a+b)^3= a^3 + b^3 + 3ab(a+b)

Answer 2

Answer:

Heya !!!

(13)³ = 2197

(8)³ = 512

And,

(21)³ = 9261.

Therefore,

(-13)³ - (8)³ + (21)³

=> -2197 - 512 + 9261

=> 9261 - (2197 + 512)

=> 9261 - (2709)

=> 9261 - 2709

=> 6552.

HOPE IT WILL HELP YOU...... :-)..

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