a)x*(y+z)=-10
3xy+3xz=?
xy+xz=-10 | *3
3(xy+xz)=3*(-10)
3xy+xz=-30
b)x=-3
y+z=6
xy+xz=? =>x*(y+z)=> -3*6=-18
c)x-y=7
z=-4
zx-zy=?
z(x-y)=> -4*7=-38
d)y=-2
x+z-t=-9
-xy-zy+ty=?
-xy-zy+ty=K | *(-1)
xy+zy-ty=-k => y(x+z-t)=-K =>
=>-2*(-9)=18=> K=-18
Deci -xy-zy+ty=-18
Sper ca te-am ajutat
