8z^2+2z-15 factor

Question

8z^2+2z-15 factor

anonymous · Answer

how about 
$$(2z+3)(4z-5)$$

anonymous · Answer

how did u get it

anonymous · Answer

One method is factor by grouping you multiply 8(-15) and you get -120 then you look for two factors of -120 that add up to the middle coefficient of your expression 2. That will be -12 and 10

anonymous · Answer

thats the only part i understand i dont know how to break it down?

anonymous · Answer

a) trial and error
b) find the zeros
c) factor by "grouping" whatever that is

anonymous · Answer

So you rewrite your equation as:
(8z^2 -12z) + (10z - 15)
And take the GCF of the both sides
4z(2z - 3z) + 5(2z - 3)
(2z - 3)(4z + 5)

anonymous · Answer

@nayeaddo, you can explain better than i can but it should be 12 and -10 right?

anonymous · Answer

Ugghh lol I messed up its 12 and -10 yes you're right.

anonymous · Answer

lol ok

anonymous · Answer

do you get it though?

anonymous · Answer

i dont know how to break it down after i put -10 and 12 into it

anonymous · Answer

Okay so you have:
(8z^2 -10z) + (12z - 15)
2z(4z - 5) + 3(4z - 5)
(4z - 5)(2z + 3)

anonymous · Answer

The order of -10z + 12z doesn't matter because:
-10z + 12z = 12z - 10z = 2z

anonymous · Answer

ok thanks

anonymous · Answer

you're welcome