multipling polynomials: (6x^2 - 7)^2 (not sure second step)

[van]

(6x^2 - 7)^2
6x^2 - 42x - 42x + 49
so, at this point when combining like terms is it:
6x^2 -84x^2 + 49

or

6x^2 - 84 + 49

thanks for your help!

[Loren]

(6x[sup:10ixzz6a]2[/sup:10ixzz6a] - 7)[sup:10ixzz6a]2[/sup:10ixzz6a] means (6x[sup:10ixzz6a]2[/sup:10ixzz6a] - 7)(6x[sup:10ixzz6a]2[/sup:10ixzz6a] - 7) just like (a[sup:10ixzz6a]2[/sup:10ixzz6a]-b)[sup:10ixzz6a]2[/sup:10ixzz6a] means (a[sup:10ixzz6a]2[/sup:10ixzz6a]-b)(a[sup:10ixzz6a]2[/sup:10ixzz6a]-b).

(a[sup:10ixzz6a]2[/sup:10ixzz6a]-b)(a[sup:10ixzz6a]2[/sup:10ixzz6a]-b) becomes a[sup:10ixzz6a]4[/sup:10ixzz6a] - 2a[sup:10ixzz6a]2[/sup:10ixzz6a]b + b[sup:10ixzz6a]2[/sup:10ixzz6a]. Apply this to your problem

P.S. (6x[sup:10ixzz6a]2[/sup:10ixzz6a])(6x[sup:10ixzz6a]2[/sup:10ixzz6a]) = 36x[sup:10ixzz6a]4[/sup:10ixzz6a]

[Subhotosh Khan]

(6x^2 - 7)^2
6x^2 - 42x - 42x + 49
so, at this point when combining like terms is it:
6x^2 -84x^2 + 49

or

6x^2 - 84 + 49

Assuming you multiplication is correct (which it is not)

None of those two:

- 42x - 42x = 84 x

However, as Loren pointed out - you have other problems .

thanks for your help!

[van]

wait a minute...
wouldn't - 42x - 42x = -84x ?

anyways, yes - i caught my mistake on the original post thanks to Loren.

[Subhotosh Khan]

wait a minute...
wouldn't - 42x - 42x = -84x ? <<< Yes indeed - you are correct

anyways, yes - i caught my mistake on the original post thanks to Loren.