2x-8y+5y-x при x 0.4 и y 2/3
2*4/10 -8*2/3 +5*2/3 -4/10= 4/5-16/3+10/3-2/5=(4-2)/5 -(16+10)/3=2/5-6/3=2/5-2=(2-10)/5=-8/5=-1*3/5