Sagot :
A=(2x-6)(7-3x)=14x-6x²-42+18x=-6x²+32x-42
B=5(8-4x)²=5(64-64x+16x²)=80x²-320x+320
C=-(-x+10)+2(x²+5)+x(8-2x)=-x+10+2x²+10+8x-2x²=7x+20
D=1/3(4x/7-3)+6/7x=4x/21-1
E=(^7+^2x)²???? de la forme (a+b)²=a²+2ab+b²
F=5x³(4x²-x⁶/5+1/x)=20x⁵-x⁹+5x²=-x⁹+20x⁵+5x²