Giúp mình với khó quá trừng à mình chuẩn bị nộp rồi có ai bt Bài này ko ạ

Đáp án:

`3) = 16x²-49`

`4) = 27y³+54y²+36y+8`

`5) = 1/8x³-15/4x²+75/2x-125`

`6) = 1/9y²+4/3y+4`

`7) = 4/9x²-28/3x+49`

`8) = 1/4x²-9`

`9) = 64x³+48x²+12x+1`

`10) 1/64x³-15/16x²+75/4x-125`

Giải thích các bước giải:

`3) (4x-7).(4x+70)`

`= (4x)²-7²`

`= 16x²-49`

`4) (3y+2)³`

`= (3y)³+3.(3y)².2+3.3y.2²+2³`

`= 27y³+54y²+36y+8`

`5) (1/2x-5)³`

`=(1/2x)³-3.(1/2x)².5+3.1/2x.5²-5³`

`= 1/8x³-15/4x²+75/2x-125`

`6) (1/3y+2)²`

`= (1/3y)²+2.1/3y.2+2²`

`= 1/9y²+4/3y+4`

`7) (2/3x-7)²`

`=(2/3x)²-2.2/3x.7+7²`

`= 4/9x²-28/3x+49`

`8) (1/2x-3).(1/2x+3)`

`= (1/2x)²-3²`

`= 1/4x²-9`

`9) (4x+1)³`

`= (4x)³+3.(4x)².1+3.4x.1²+1³`

`= 64x³+48x²+12x+1`

`10) (1/4x-5)³`

`= (1/4x)³-3.(1/4x)².5+3.1/4x.5²-5³`

`= 1/64x³-15/16x²+75/4x-125`