SOLUTION: Can someone please help, I am totally lost Find all x-intercepts of the given function f(x). F(x)=x-17√(x+72) Thank you.

Algebra ->  Quadratic Equations and Parabolas -> SOLUTION: Can someone please help, I am totally lost Find all x-intercepts of the given function f(x). F(x)=x-17√(x+72) Thank you.      Log On


   

Question 457775: Can someone please help, I am totally lost
Find all x-intercepts of the given function f(x).
F(x)=x-17√(x+72)
Thank you.
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
F(x) = x - 17√(x+72)
See if we can put it into ax^2 + bx + c form
x = 17sqrt%28x%2B72%29
Square both sides
x^2 = 289*(x+72)
x^2 = 289x + 20808
x^2 - 289x - 20808 = 0
Solve for x using the quadratic formula
x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+
a=1; b=-289, c=-20808
x+=+%28-%28-289%29+%2B-+sqrt%28-289%5E2-4%2A1%2A-20808+%29%29%2F%282%2A1%29+
:
x+=+%28289+%2B-+sqrt%2883521%2B83232+%29%29%2F2+
:
x+=+%28289+%2B-+sqrt%28166753+%29%29%2F2+
Two solutions
x+=+%28289+%2B+408.354%29%2F2+
x = 697.354%2F2
x = 348.677
and
x+=+%28289+-+408.354%29%2F2+
x = %28-119.354%29%2F2
x = -59.677
:
Check both these solutions in the original equation, only x=348.677 is an intercept