SOLUTION: Solve for x. {{{4x(x-9)-5x(x-8)=-5}}} x=____ Simplify your answer. Use a comma to separate answers as needed.

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: Solve for x. {{{4x(x-9)-5x(x-8)=-5}}} x=____ Simplify your answer. Use a comma to separate answers as needed.       Log On


   



Question 397255: Solve for x.
4x%28x-9%29-5x%28x-8%29=-5
x=____
Simplify your answer. Use a comma to separate answers as needed.

Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!

4x%28x-9%29-5x%28x-8%29=-5
4x%5E2+-4x%2A9-5x%5E2+-5x%2A%28-8%29+=-5
4x%5E2+-36x+-5x%5E2+%2B40x+=-5

-x%5E2+%2B4x+=+-5
-x%5E2+%2B4x+%2B+5+=+0......use quadratic formula

Solved by pluggable solver: Quadratic Formula
Let's use the quadratic formula to solve for x:


Starting with the general quadratic


ax%5E2%2Bbx%2Bc=0


the general solution using the quadratic equation is:


x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29




So lets solve -x%5E2%2B4%2Ax%2B5=0 ( notice a=-1, b=4, and c=5)





x+=+%28-4+%2B-+sqrt%28+%284%29%5E2-4%2A-1%2A5+%29%29%2F%282%2A-1%29 Plug in a=-1, b=4, and c=5




x+=+%28-4+%2B-+sqrt%28+16-4%2A-1%2A5+%29%29%2F%282%2A-1%29 Square 4 to get 16




x+=+%28-4+%2B-+sqrt%28+16%2B20+%29%29%2F%282%2A-1%29 Multiply -4%2A5%2A-1 to get 20




x+=+%28-4+%2B-+sqrt%28+36+%29%29%2F%282%2A-1%29 Combine like terms in the radicand (everything under the square root)




x+=+%28-4+%2B-+6%29%2F%282%2A-1%29 Simplify the square root (note: If you need help with simplifying the square root, check out this solver)




x+=+%28-4+%2B-+6%29%2F-2 Multiply 2 and -1 to get -2


So now the expression breaks down into two parts


x+=+%28-4+%2B+6%29%2F-2 or x+=+%28-4+-+6%29%2F-2


Lets look at the first part:


x=%28-4+%2B+6%29%2F-2


x=2%2F-2 Add the terms in the numerator

x=-1 Divide


So one answer is

x=-1




Now lets look at the second part:


x=%28-4+-+6%29%2F-2


x=-10%2F-2 Subtract the terms in the numerator

x=5 Divide


So another answer is

x=5


So our solutions are:

x=-1 or x=5