(x+1)^3-y^3 (1 Viewer)

[ta1g]

I know the answer to this but do not understand the concept of it.

answer is (x+1-y)(x^2+2x+1+xy+y+y^2)

a few other simpler examples might help me..Thanks

 

[Trev]

There's a rule: (a+b)³ = (a+b)(a²-ab+b²) [aswell as; (a-b)³ = (a-b)(a²+ab+b²).
It works out from that:
(x+1)³-y³ = (x+1-y)((x+1)²+y(x+1)+y²) etc.

 

[ta1g]

ok thanks alot

 

[SaHbEeWaH]

There's a rule: (a+b)³ = (a+b)(a²-ab+b²) [aswell as; (a-b)³ = (a-b)(a²+ab+b²).
It works out from that:
(x+1)³-y³ = (x+1-y)((x+1)²+y(x+1)+y²) etc.

You are confusing this with the difference of two cubes.
(a + b)³ = (a + b)(a² + 2ab + b²) = a³ + 3ba² + 3ab² + b³

to solve that try this:

let m = x + 1
m³ - y³ = (m - y)(m² + my + y²)
and substitute

 

[Trev]

Same thing

 

[want2beSMART]

lol

sorry trev, but some people have simple minds