Question

Solve 4x2 = 12x + 40.
i can't find the two numbers -____-

Answer 1

Is that 4 times 2 or 4x times 2?

Answer 2

4x^2
2 is the exponent of x

Answer 3

ok

Answer 4

so it is a quadratic? 4x^2-12x+40=0

Answer 5

4x² -12 x - 40 = 0 | divde by 4
x² - 3x - 10 = 0
x²-3x-10 = (x-5) * (x+2)

Hence your roots are 5 and -2

Answer 6

@Stiwan but it's a quadratic.and -5 and 2 added don't equal -40 and multiplied don't equal -12?

Answer 7

@jess_in_tenesee yes

Answer 8

try plugging it into the quadratic formula?

Answer 9

Did you remember you factored out 4?

Answer 10

oooooh! that's why! i forgot to factor 4. ok hold on let me try that

Answer 11

LOL

Answer 12

lol ok so my final answer is x=5 and x=-2 (:

Answer 13

That's because x^2 - 3x - 10 was factored, not 4x^2 - 12x - 40. If you factor
4x^2 - 12x - 40, you get:
4x^2 - 12x - 40
4x^2 - 20x + 8x - 40
4x(x - 5) + 8(x - 5)
(4x + 8)(x - 5) Notice, from this you get back to the original quadratic. -20 and 8 are your two numbers.

But that simplifies further to
4(x + 2)(x - 5)

Answer 14

Your two numbers need to multiply to get -160 and add to get -12

a + b = -12
ab = 4(-40)

Answer 15

Thank you ! (: @Hero