SOLUTION: Use the quadratic formula to solve the equation. 3x^2-36x=72 The answer is going to be 18 + or - the square root of something over 3.

Algebra ->  Quadratic Equations and Parabolas -> SOLUTION: Use the quadratic formula to solve the equation. 3x^2-36x=72 The answer is going to be 18 + or - the square root of something over 3.      Log On


   

Question 161241: Use the quadratic formula to solve the equation.
3x^2-36x=72
The answer is going to be 18 + or - the square root of something over 3.
Answer by KnightOwlTutor(293) About Me  (Show Source):
You can put this solution on YOUR website!
3x^2-36x=72
The first step is to subtract 72 from both sides
3x^2-36x-72=0


Solved by pluggable solver: SOLVE quadratic equation with variable
Quadratic equation ax%5E2%2Bbx%2Bc=0 (in our case 3x%5E2%2B-36x%2B-72+=+0) has the following solutons:

x%5B12%5D+=+%28b%2B-sqrt%28+b%5E2-4ac+%29%29%2F2%5Ca

For these solutions to exist, the discriminant b%5E2-4ac should not be a negative number.

First, we need to compute the discriminant b%5E2-4ac: b%5E2-4ac=%28-36%29%5E2-4%2A3%2A-72=2160.

Discriminant d=2160 is greater than zero. That means that there are two solutions: +x%5B12%5D+=+%28--36%2B-sqrt%28+2160+%29%29%2F2%5Ca.

x%5B1%5D+=+%28-%28-36%29%2Bsqrt%28+2160+%29%29%2F2%5C3+=+13.7459666924148
x%5B2%5D+=+%28-%28-36%29-sqrt%28+2160+%29%29%2F2%5C3+=+-1.74596669241483

Quadratic expression 3x%5E2%2B-36x%2B-72 can be factored:
3x%5E2%2B-36x%2B-72+=+3%28x-13.7459666924148%29%2A%28x--1.74596669241483%29
Again, the answer is: 13.7459666924148, -1.74596669241483. Here's your graph:
graph%28+500%2C+500%2C+-10%2C+10%2C+-20%2C+20%2C+3%2Ax%5E2%2B-36%2Ax%2B-72+%29