easy
g(x+a)
sub x+a for every x in equation
g(x+a)=-5(x+a)^2-3(x+a)+2
g(x+a)=-5(x²+2xa+a²)-3x-3a+2
g(x+a)=-5x²-10xa-5a²-3x-3a+2
so now minus g(x)
g(x+a)-g(x)=
-5x²-10xa-5a²-3x-3a+2-(-5x²-3x+2)=
-5x²-10xa-5a²-3x-3a+2+5x²+3x-2=
-5x²+5x²-10xa-5a²-3x+3x-3a+2-2=
-10xa-5a²-3a
g(x+a)-g(x)=-5a²-10xa-3a
