Question

I need to finish this problem and I'm not sure if I look for the lcm or the gcm. This is what I have so far: 4x(x-9)-5x(x-8)=-5 4x^2-36x-5x^2+40x+5=0

Answer 1

4x(x-9)-5x(x-8) = 0

that distributed out is equal to

4x^2 - 36x - 5x^2 + 40x = 0

combine like terms

-x^2 + 4x = 0
factor again
-x(x - 4) = 0

and solve each factor for 0

-x = 0
x - 4 = 0

x = 0, 4

Answer 2

When you combine like terms, are you adding or multiplying them? I don't remember the process.

Answer 3

4x^2 - 36x - 5x^2 + 40x = 0

if you were to combine these terms together, it would look like this (basically a re-arranging of the equation):

4x^2 - 36x - 5x^2 + 40x = 0
(4x^2 - 5x^2) - (36x + 40x) = 0
(4-5)*(x^2 - (36-40)x = 0
-1x^2 - 4x = 0
-x^2 - 4x = 0
etc.

Answer 4

and that should actually say this:

(4-5)*x^2 - (36+40)x = 0
-1x^2 - 4x = 0
-x^2 - 4x = 0

from the 3rd line down. cause 40 was never negative! woops.

Answer 5

Okay one more question then, -(36+40) would become a positve 4, or do you switch the signs inside of the paranthesis because there is a negative in front of them?

Answer 6

I know I'm missing something simple here :(

Answer 7

my error again...

4x^2 - 36x - 5x^2 + 40x = 0 <--- wrong
(4x^2 - 5x^2) - (36x + 40x) = 0 <---wrong

is actually

4x^2 - 36x - 5x^2 + 40x = 0
(4x^2 - 5x^2) - (-36x + 40x) = 0 <--- correct (-36 + 40 = 4

(-1)(x^2) + (-4)(x) = 0
-x^2 - 4x = 0
etc.

so IN ALL.

4x^2 - 36x - 5x^2 + 40x = 0
(4-5)*x^2 - (-36+40)x = 0
(-1)x^2 - (4)x = 0
-x^2 - 4x = 0
-x^2 - 4x = 0
etc.

man took me awhile to find that error. I didn't keep -36 negative, and then didn't multiply it by a negative factor again.

Answer 8

O.o Lol, okay so when I simplify that I will have x= X^2 and x = 4x ?