SOLUTION: original problem: 5x^2-30x+40=0 work: 5x^2-30x=-40 x^2-6x=-8 x^2-6x+9=-8+9 Please help. I keep getting lost. Could you show me how to work this problem s

Algebra ->  Algebra  -> Quadratic Equations and Parabolas  -> Quadratic Equation Customizable Word Problems -> SOLUTION: original problem: 5x^2-30x+40=0 work: 5x^2-30x=-40 x^2-6x=-8 x^2-6x+9=-8+9 Please help. I keep getting lost. Could you show me how to work this problem s      Log On

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Question 119488: original problem: 5x^2-30x+40=0
work:
5x^2-30x=-40
x^2-6x=-8
x^2-6x+9=-8+9
Please help. I keep getting lost. Could you show me how to work this problem step by step? I already have the answer, so I'm not looking for that, just how to do it. The answer is x=2, x=4
Found 2 solutions by stanbon, Earlsdon:
Answer by stanbon(57410) About Me  (Show Source):
You can put this solution on YOUR website!
original problem: 5x^2-30x+40=0
work:
5x^2-30x=-40
x^2-6x=-8
x^2-6x+9=-8+9
Factor to get:
(x-3)^2 = 1
Take the square root of both sides to get;
x-3=1 or x-3=-1
x = 4 or x = 2
====================
Cheers,
Stan H.

Answer by Earlsdon(6287) About Me  (Show Source):
You can put this solution on YOUR website!
Solve for x:
5x%5E2-30x%2B40+=+0 First, you can factor a 5 from this quadratic equation.
5%28x%5E2-6x%2B8%29+=+0 Now apply the "zero product principle": Ifa%2Ab+=+0then eithera+=+0orb+=+0 or both.
So...
If 5%28x%5E2-6x%2B8%29+=+0then either 5+=+0 (obviously not true!) or x%5E2-6x%2B8+=+0. Ok, so...
x%5E2-6x%2B8+=+0 Solve this by factoring:
%28x-2%29%28x-4%29+=+0 ...again, apply the "zero product principle"...
If x-2+=+0 then x+=+2 or
If x-4+=+0 then x+=+4
The solutions are, as you have stated, x = 2 or x = 4.