Answer:
a S(-3) = 2(-3)(-3)+5(-3)-12
=18-15-12
=-9
b 2x2+5x-12=0
2x2+8x-3x-12=0
2x(x-4)-3(x+4)=0
(2x-3)(x+4)=0
2x-3=0
x=3/2
x=-4
sorry I couldn't answer the other question
