SOLUTION: What is the answer to x^2-7x-8=0

Algebra ->  Quadratic Equations and Parabolas  -> Quadratic Equations Lessons  -> Quadratic Equation Lesson -> SOLUTION: What is the answer to x^2-7x-8=0      Log On


   

Question 445514: What is the answer to x^2-7x-8=0
Found 3 solutions by rwm, stanbon, josmiceli:
Answer by rwm(914) About Me  (Show Source):
You can put this solution on YOUR website!
what are the factors of -8 which add up to -7
-8 and 1
(x-8)*(x+1)=0
x=8 x=-1

Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
What is the answer to x^2-7x-8=0
------------
Factor using inverse FOIL:
x^2-8x+x-8 = 0
Factor:
x(x-8)-(x-8) = 0
----
(x-8)(x-1) = 0
X = 8 or x = 1
===================
Cheers,
Stan H.
=========

Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
+x%5E2-7x-8=0+
Use the quadratic equation
x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+
+a+=+1+
+b+=+-7+
+c+=+-8+
x+=+%28-%28-7%29+%2B-+sqrt%28+%28-7%29%5E2-4%2A1%2A%28-8%29+%29%29%2F%282%2A1%29+
x+=+%28+7+%2B-+sqrt%28+49+%2B+32%29%29+%2F+2+
x+=+%28+7+%2B-+sqrt%28+81%29%29+%2F+2+
x+=+%28+7+%2B+9+%29+%2F+2+
+x+=+8+
and
x+=+%28+7+-+9+%29+%2F+2+
+x+=+-1+
-------------
check answers:
+x+=+-1+
+x%5E2-7x-8=0+
+%28-1%29%5E2-7%2A%28-1%29-8=0+
+1+%2B+7+-+8+=+0+
+0+=+0+
You can check other answer