<span>4 х-1 =1</span>
20y-20x=xy
x=14-2y
20y-20*(14-2y)=y*(14-2y)
10y-140+20y=7y-y^2
y^2-23y+140=0
y1=(23+3)/2=13
y2=(23-3)/2=10
x1=14-26=-12
x2=14-20=-6
2)
4ав^3-a^3в=4ав(в2-а2)=4ав(в-а)(в+а)
-9в-6в^3-в^3=-(9в-6в^3-в^3)=-(3в-в)^2