(x-4y)²-(4x-y)²= x²-8xy+16y²-16x²+8xy-y²= -15x²+15y²= -15(x²-y²)
1 1/3= 4/3
-15(16/9-4)= -15(-20/9)= 300/9= 100/3= 33 1/3
(x-4y-(4x-y))*(x-4y+(4x-y))=-15(x+y)*(x-y)
(x-4y)²-(4x-y)²= x²-8xy+16y²-16x²+8xy-y²= -15x²+15y²= -15(x²-y²)
1 1/3= 4/3
-15(16/9-4)= -15(-20/9)= 300/9= 100/3= 33 1/3
(x-4y-(4x-y))*(x-4y+(4x-y))=-15(x+y)*(x-y)