Question

how would you factor 4z^2 - 16z + 15?? i multiplied 4 and 15 to get 60 but i'm not getting any numbers whose product is 60 and sum is -16

Answer 1

-10, -6 ?

Answer 2

oh! derp!

Answer 3

thanks yam lol

Answer 4

Haha. You're welcome.

Answer 5

The way I would do it is write the pairs of factors for 4
1,4
2,2

and for 15
1,15
3,5

the + sign on the 15 means both roots have the same sign. the minus on -16 means both will be negative.

now try combinations
example: 1,4 and 1,15 might give 4*1 + 1*15 which does not work

however
2,2 and 3,5 gives 2*6+2*5 = 16

as mentioned above both roots are negative, so
(2x -3)(2x-5) is the answer