(21+m)^3 help?!?!?!?

Question

I think (i just think) its using this formula but i'm not sure how to get the answer: (a+b)^3=a^3+b^3+3ab(a+b)

the anwer is supposed to be : l^3+m^3+3l^2m+3lm^2

sorry i meant (2l+m)^3

I MEANT (2l+m)^3 !!!!!!!!!!!!!!!!!

hope that got your attention

Answer 1

(2I+m)^3=(2I+m)(2I+m)^2
=(2I+m)[(2I)^2+2*2I*m+m^2]
=(2I+m)(4I^2+4Im+m^2)
=2I*4I^2+2I*4Im+2I*m^2+m*4I^2+m*4Im+m*m^2
=8I^3+8I^2*m+2Im^2+4I^2*m+4Im^2+m^3
=8I^3+m^3+6Im^2+12I^2*m

Answer 2

(2 l + m) ( 4 l ² + 4 l m + m ² )

8 l ³ + 8 l ² m + 2 l m ²
_____4 l ² m + 4 l m ² + m ³

8 l ³ + 12 l ² m + 6 l m ² + m ³

Which does not agree with answer you quote?

Answer 3

(2l+m)^3 = (2l)^3 + 3(2l)^2m + 3(2l)m^2 + m^3
= 8l^3 + 12l^2m + 6lm^2 + m^3

Answer 4

(21+m)^3 (using the equation above a is 21, and b is m)
(21)^3+m^3+3(21)^2(m)+(3)(21)m^2
=
9261+m^3+1323m+63m^2

Answer 5

You don't need to use the formula if you forget than use basic thing about power which is
(21+m)^3
= (21 + m) * (21 + m) * (21 + m)
= (21*21 + 21*m + m*21 + m*m) * (21 + m)
= (441 + 42m + m^2) * (21 + m)
= 21 * 441 + 21 * 42m + 21*m^2 + m*441 + m*42m + m*m^2
= 9261 + 882m + 21m^2 + 441m + 42m^2 + m^3
= m^3 + 63m^2 + 1323m + 9261
for your final answer just simply my result

Answer 6

the formula you should use reads
(a+b)^3=aaa+bbb+3aab+3bba

Answer 7

Add 21 to m and multiply the result 3 times

(21+m)x(21+m)x(21+m) = Result

Answer 8

(2 l+m)^3

= 8l^3 + m^3 + 12 l^2 m + 6l m^2