SOLUTION: factors of -15=-8x2+2x

Algebra ->  Expressions -> SOLUTION: factors of -15=-8x2+2x      Log On


   

Question 1039204: factors of -15=-8x2+2x
Found 3 solutions by josgarithmetic, ikleyn, MathTherapy:
Answer by josgarithmetic(39625) About Me  (Show Source):
You can put this solution on YOUR website!
-15=-8x2%2B2x

8x%5E2-2x-15=0

Trying combinations and checking each might be a way, but easier maybe to use general solution formula for quadratic equation.
Discriminant, %28-2%29%5E2-4%2A8%2A%28-15%29=4%2B4%2A8%2A15=4%2B60%2A8=4%2B640=644=161%2A4

x=%282%2B-+sqrt%28161%2A4%29%29%2F%282%2A8%29

x=%281%2B-+sqrt%28161%29%29%2F8

%28x-%28%281%2Bsqrt%28161%29%29%2F8%29%29%28x-%28%281-sqrt%28161%29%29%2F8%29%29=0

%28x-1-sqrt%28161%29%2F8%29%28x-1%2Bsqrt%28161%29%2F8%29=0

Answer by ikleyn(52847) About Me  (Show Source):
You can put this solution on YOUR website!
.
factors of -15=-8x2+2x
~~~~~~~~~~~~~~~~~~~~~~~ 

-15 = -8x%5E2+%2B+2x,

8x%5E2+-+2x+-+15 = 0,

x%5B1%2C2%5D = %282+%2B-+sqrt%284+%2B+4%2A8%2A15%29%29%2F16 = %282+%2B-+sqrt%28484%29%29%2F16 = %282+%2B-+22%29%2F16.

x%5B1%5D = 24%2F16 = 3%2F2,  x%5B2%5D = -20%2F16 = -5%2F4.


Factorization:  8x%5E2+-+2x+-+15 = 8%28x-3%2F2%29%2A%28x%2B5%2F4%29 = (2x-3)*(4x+5).


Answer by MathTherapy(10555) About Me  (Show Source):
You can put this solution on YOUR website!

factors of -15=-8x2+2x
-+15+=+-+8x%5E2+%2B+2x

8x%5E2+-+2x+-+15+=+0

8x%5E2+-+12x+%2B+10x+-+15+=+0 ------- Replacing - 2x with - 12x + 10x

4x%282x+-+3%29+%2B+5%282x+-+3%29+=+0

highlight_green%28%284x+%2B+5%29%282x+-+3%29+=+0%29