Question

One question is all I need help on.

Answer 1

Hello,

y=x²+2x
y=3x+20

==>x²+2x=3x+20
==>x²+2x-3x-20=0
==>x²-x-20=0
==>x²-2*1/2*x+1/4-20-1/4=0
==>(x-1/2)²-81/4=0
==>(x-1/2-9/2)(x-1/2+9/2)=0
==>(x-5)(x+4)=0
==>(x=5 and y= 35 ) or (x=-4 and y=-8)