1. ## square

help im stuck
is this possible to factorise?
3(x^2-10x+16)

= (x+10)(x-8) ???

2. ## Re: square

This is obviously not correct as there was a factor of 3 that disappeared.

I think you'll find that the two numbers that multiply to give 16 and add to give -10 are -8 and -2.

3. ## Re: square

Originally Posted by dragon555
help im stuck
is this possible to factorise?
3(x^2-10x+16)

= (x+10)(x-8) ???
Since 10(-8)= -80 is NOT 3(16)= 48, no those are obviously not the same.

You could do it this way: $x^2- 10x+ 16= x^2- 10x+ 25- 9= (x- 5)^2- 9$ which is a "sum and difference of squares"- it is equal to $((x-5)+3)((x-5)-3)= (x-2)(x-8)$.

$3(x^2- 10x+ 16)= 3(x- 2)(x- 8)$