where does the parabola y=x^2+4x-9 intersect the line y=4x

Question

i need coordinates not equations please

Answer 1

(-3,-12), (3, 12)

Answer 2

The equations intersect where they are equal to each other.

 

x²+4x-9=4x

Solve for x

 

x² +4x -4x-9=0

x²-9=0

This is the difference of two squares:  x²-3²=0

(a²-b²)= (a-b)(a+b)

 

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

Either x-3=0   or    x+3=0

          x=3     or    x=-3

 

if x=3 then 4x=12

if x=-3 then 4x=-12

 

The graphs intersect at the points (3,12), (-3,-12)

 

check:  x²+4x-9=4x

           (-3)² +4(-3)-9 = 4(-3)

            9-12-9=-12

              -12=-12

 

          3²+4(3)-9=4(3)

           9+12-9=12

             12=12

 

the answers check as correct.