Find the expansion of (r+4)^3?

Question

How do i work this?

Answer 1

hello there,
The general formula is: -
(a+b)^3 = a^3+b^3+3ab(a+b)
or
(a+b)^3=a^3+b^3+3a^2b+3*a*b^2 (if you prefer it in expanded form)

(r+4)^3 = r^3+4^3+3*r^2*4+3*r*4^2
= r^3+64+12r^2+48r

The formula comes in handy if you can manage to remember it.

P.S: Soz, I know it looks more complicated than it actually is. Try puttin' it on a paper, looks much better then.

Hope this helps

Cheers
-Steff

Answer 2

ok, so here is how you do it:

(r+4)^3 = (r+4)(r+4)(r+4)

(r+4)(r+4) = First.Outer.Inner.Last. = F.O.I.L.

= r^2 + 4r + 4r + 16 = r^2 + 8r + 16

(r+4)(r+4)(r+4) = (r^2 + 8r + 16)(r + 4) again, foil (or you can call

it distribution in this case.)

(r^2 + 8r + 16)(r + 4) = r^3 + 8r^2 + 16r + 4r^2 + 32r + 64

now combine like terms= r^3 + 12r^2 + 48r + 64

Answer 3

this is the same as

(r+4)(r+4)(r+4)

(r^2 + 8r + 16)(r+4)

r^3 + 12r^2 +48r + 64

Answer 4

r^2 + 8r + 16 (r+4)
----------------
r^3 + 8r^2 + 16r + 4r^2 + 32r + 64
--------------------------
final = r^3 + 12r^2 + 48r + 64

Answer 5

iono