Question 40823
y=-2x^2+8x+27
2x+y=15      (move 2x to the right of the equation to leave y alone)
y=15-2x      in the first equation write (15-2x)instead of y;

15-2x=-2x^2+8x+27
2x^2-2x-8x+15-27=0
2x^2-10x-12=0     factor out 2 from the trinomial;
2(x^2-5x-6)=0      divide both sides by 2;
x^2-5x-6=0
(x-6)(x+1)=0
x-6=0
x=6  and

x+1=0
x=-1

To find the values of y, we plug in the values of x in ne of the given equations;
for x=6;
2.6+y=15
12+y=15
y=15-12
y=3    and

forx=-1
2.(-1)+y=15
-2+y=15
y=15+2
y=17