SOLUTION: Find the x intercepts and y intercepts f(x)=-x^2+3x+28

Algebra ->  Rational-functions -> SOLUTION: Find the x intercepts and y intercepts f(x)=-x^2+3x+28      Log On


   

Question 489262: Find the x intercepts and y intercepts
f(x)=-x^2+3x+28
Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!
f%28x%29=-x%5E2%2B3x%2B28
to find the x-intercept: set f%28x%29=0
0=-x%5E2%2B3x%2B28...use quadratic formula

x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+ ...a=-1, b=3, and c=28

x+=+%28-3+%2B-+sqrt%28+3%5E2-4%2A%28-1%29%2A28+%29%29%2F%282%2A%28-1%29%29+

x+=+%28-3+%2B-+sqrt%28+9%2B4%2A28+%29%29%2F%28-2%29+

x+=+%28-3+%2B-+sqrt%28+112%29%29%2F%28-2%29+

x+=+%28-3+%2B-+10.58%29%2F%28-2%29+
solutions:
x+=+%28-3+%2B10.58%29%2F%28-2%29+
x+=+%287.58%29%2F%28-2%29+
x+=+-3.79+...round it to whole number
x+=+-4+
or
x+=+%28-3+-10.58%29%2F%28-2%29+
x+=+%28-13.58%29%2F%28-2%29+
x+=+6.79+..round it to whole number
x+=+7+
to find the y-intercept: set x=0
f%28x%29=-0%5E2%2B3%2A0%2B28
f%28x%29=28
let see it on a graph
+graph%28+500%2C+500%2C+-15%2C+15%2C+-10%2C+35%2C+-x%5E2%2B3x%2B28%29+