(6x+7)²
⇔(6x)²+ 2.7.6x+7²
(1-3x)²
⇔1²-2.3x+3²
(x+10)³
⇔ x³+3x².3+3x.3²+3³
(2-x)³
⇔ 2³-3.2².x+3.2.x²-x³
(3x+1)³
⇔ (3x)³+3.(3x)³.1+3.3x.1³+1³
2
A=(2x-y)²+(2x+y)²
A= (2x)²-2.2x.y+y²+(2x)²+2.2x.y+y²
A= 4x²-4xy+y²+4x²+4xy+y²
A=8x²+2y² thay số ta có
A=8.(-1/2)²+2.(-0,3)²
A=8.1/4+2.0,09
A=2,18
B=(3x-y)²-(3x-y)²
B=(3x-y+3x-y).[(3x-y)-(3x-y)]
B=(3x-y+3x-y).0
⇒B=0 với mọi x