a) x=2 ; y=-2
3x(2x+y)-2y(-x-y)=6x²+3xy-2xy+2y²=6x²+2y²+xy
Podstawiamy:
6x²+2y²+xy=6*2²+2*(-2)²+2*(-2)=6*4+2*4-4=24+8-4=32-4=28
b) a=3/2 ; b=1/5
-2a(-a-b)+3a(a+b)=2a²+2b²+3a²+3ab=5a²+2b²+3ab
Podstawiamy:
5a²+2b²+3ab=5*(3/2)²+2*(1/5)²+3*3/2*1/5=5*9/4+2*1/25+9/10=45/4+2/25+9/10=
1125/100+8/100+90/100=1223/100=12 23/100