SOLUTION: 5x^2-5x-100=0 Pls step by step

Algebra ->  Test -> SOLUTION: 5x^2-5x-100=0 Pls step by step      Log On


   

Question 351550: 5x^2-5x-100=0
Pls step by step
Found 2 solutions by Fombitz, ewatrrr:
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
5x%5E2-5x-100=0
Divide both sides by 5.
x%5E2-x-20=0
Factor.
%28x-5%29%28x%2B4%29=0
Use the zero product property to find the two solutions.
x-5=0
highlight%28x=5%29
.
.
.
x%2B4=0
highlight%28x=-4%29

Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!
Hi,
*Note: quadratic equations may be solved by factoring directly, if possible, or by using the quadratic equation to solve.
.
5x^2-5x-100=0
.
Can we factor this simply and directly?
(5x ... a)(x ...b)
What are the common mutiples of 100?? 10*10, 2*50, 25*4
would any these combinations work to gve us the desired result?
.
5x^2-5x-100=0
(5x -25)(x + 4) = 0
(5x - 25) = 0
x = 5
or
(x + 4) = 0
x = -4
.
Using the quadratic equation
x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+
x+=+%28-%28-5%29+%2B-+sqrt%28+%28-5%29%5E2-4%2A5%2A100+%29%29%2F%282%2A5%29+
.
x+=+%285+%2B-+sqrt%282025+%29%29%2F10+
x+=+%285+%2B-+45%29%2F10+
.
x = 50/10 = 5
or
x = -40/10 = -4