Упрости и реши -4(8х-9у)+5(6х-4у) при х=0.8 у = 0.9
-4(8х-9у)+5(6х-4у)=-32x+36y+30x-20y=16y-2x при х=0.8 у = 0.9 16*0.9-2*0.8=14.4-1.6=12.8
-4(8x-9y)+5(6x-4y) -32x+36y+30x-20y -2x+16y -2*(0.8)+16*0.9=-1.6+14.4=12.8