SOLUTION: Can you help me with this problem? Determine any axis intercepts. y = x2 + 4x − 21 / x + 7 ...How would I figure this out? ..Thank you!

Algebra ->  Equations -> SOLUTION: Can you help me with this problem? Determine any axis intercepts. y = x2 + 4x − 21 / x + 7 ...How would I figure this out? ..Thank you!      Log On


   

Question 782096: Can you help me with this problem?
Determine any axis intercepts.
y = x2 + 4x − 21 / x + 7

...How would I figure this out? ..Thank you!
Answer by fcabanski(1391) About Me  (Show Source):
You can put this solution on YOUR website!
Set x=0 to find y intercepts.


y = (0^2 +4(0)-21)/(0+7) = -21/7 = -3


For a rational function, f(x)/g(x), set f(x) = 0. Solve for x. That gives you possible x intercepts (roots). Check each number (possible x intercept) with the original equation, to make sure it doesn't make the denominator 0. If it does, discard it.


x%5E2+%2B+4x+-21+=+0


(x+7)(x-3) = 0


x+7 = 0 so x=-7. But - 7 makes the denominator 0, so discard it.


x-3 = 0 so x = 3


x=3 is the only x intercept.