help factoring!!
the problem is -16x2 + 60x + 16 then i factored the GCF of -4 and got -4(4x^2 - 15x - 4) but i can't seem to find nmbers that multiply to -4 and add to -15. am i right? or is multiply to 15 and add to 4? i need to find the zeros.

Question

help factoring!!
the problem is  -16x2 + 60x + 16 then i factored the GCF of -4 and got -4(4x^2 - 15x - 4) but i can't seem to find nmbers that multiply to -4 and add to -15. am i right? or is multiply to 15 and add to 4? i need to find the zeros.

anonymous · Answer

@math&ing001

anonymous · Answer

@jim_thompson5910

myininaya · Answer

multiply to be -16 and add up to be -15 is what you mean?

anonymous · Answer

yea, i need to split the middle term

myininaya · Answer

well what is -16(1) and -16+1 equal to?

anonymous · Answer

original: -16x2 + 60x + 16
my gess after factoring GCF: -4(4x^2 - 15x - 4)

anonymous · Answer

no, is -15 and -4

myininaya · Answer

no...You are to find two factors of a*c that have product ac and sum b.

myininaya · Answer

you need to find two number that multiply to be -16 and add up to be -15

anonymous · Answer

ohh.....

anonymous · Answer

thanks, i was in the wrong path lol

myininaya · Answer

not entirely you were able to factor out that -4 from the start :)

anonymous · Answer

lol true, well thank you!!

myininaya · Answer

let me know if you have trouble

anonymous · Answer

okay i get: -4(4x+1)(x-4)
correct me if im wrong, im supposed to find the zeros...
4, -1/4, and 4 ?

anonymous · Answer

@myininaya

myininaya · Answer

looks great! :)

myininaya · Answer

and the zeros...why do you have three of them

anonymous · Answer

because -4 is factored out the parenthesis and i equaled to it zero

myininaya · Answer

one is just a repetition 
but the x=4 only occurs once 

so you have the zeros are x=-1/4 or x=4

myininaya · Answer

-4 can never be 0

myininaya · Answer

4x+1 can be zero
x-4 can be zero
but -4 can never be zero

anonymous · Answer

oh okay i see

myininaya · Answer

i still think you did pretty well so i will give you a medal for your hard and good work

anonymous · Answer

one more, correct me if im wrong, since the leading is negative, the parabola is going to open.... down?

anonymous · Answer

thanks

myininaya · Answer

very good

anonymous · Answer

just making sure the info was frozen in my head, had to take this exam a few days ago so needed a refresher

myininaya · Answer

|dw:1411170803194:dw|
it has two x-intercepts x=4 and x=-1/4 as the graph shows
and it is open down because the number in front of the x^2 is neg

anonymous · Answer

i see

anonymous · Answer

yea the zeros are x-intercepts