SOLUTION: Find the X intercepts, and y intercepts. -x^2+5x+36 I know that I have to factor 36, to get my x intercepts, so I came up with (-6,0),(6,0) But my assignment tells m

Algebra ->  Linear-equations -> SOLUTION: Find the X intercepts, and y intercepts. -x^2+5x+36 I know that I have to factor 36, to get my x intercepts, so I came up with (-6,0),(6,0) But my assignment tells m      Log On


   

Question 266634: Find the X intercepts, and y intercepts.
-x^2+5x+36
I know that I have to factor 36, to get my x intercepts, so I came up with
(-6,0),(6,0)
But my assignment tells me this is wrong.
I believe that the y intercept would be
(0,36), is this correct?
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
To find the x-intercept(s), you need to set the expression equal to zero and solve for 'x'


-x%5E2%2B5x%2B36=0 Set the expression equal to zero.


Notice that the quadratic -x%5E2%2B5x%2B36 is in the form of Ax%5E2%2BBx%2BC where A=-1, B=5, and C=36


Let's use the quadratic formula to solve for "x":


x+=+%28-B+%2B-+sqrt%28+B%5E2-4AC+%29%29%2F%282A%29 Start with the quadratic formula


x+=+%28-%285%29+%2B-+sqrt%28+%285%29%5E2-4%28-1%29%2836%29+%29%29%2F%282%28-1%29%29 Plug in A=-1, B=5, and C=36


x+=+%28-5+%2B-+sqrt%28+25-4%28-1%29%2836%29+%29%29%2F%282%28-1%29%29 Square 5 to get 25.


x+=+%28-5+%2B-+sqrt%28+25--144+%29%29%2F%282%28-1%29%29 Multiply 4%28-1%29%2836%29 to get -144


x+=+%28-5+%2B-+sqrt%28+25%2B144+%29%29%2F%282%28-1%29%29 Rewrite sqrt%2825--144%29 as sqrt%2825%2B144%29


x+=+%28-5+%2B-+sqrt%28+169+%29%29%2F%282%28-1%29%29 Add 25 to 144 to get 169


x+=+%28-5+%2B-+sqrt%28+169+%29%29%2F%28-2%29 Multiply 2 and -1 to get -2.


x+=+%28-5+%2B-+13%29%2F%28-2%29 Take the square root of 169 to get 13.


x+=+%28-5+%2B+13%29%2F%28-2%29 or x+=+%28-5+-+13%29%2F%28-2%29 Break up the expression.


x+=+%288%29%2F%28-2%29 or x+=++%28-18%29%2F%28-2%29 Combine like terms.


x+=+-4 or x+=+9 Simplify.


So the solutions are x+=+-4 or x+=+9


So this means that the x-intercepts are (-4,0) and (9,0)


For the y-intercept, you are correct. The y-intercept is (0,36)