làm giúp 2 bài đầu với

Bài toán 9:

`a)35²-15²`

`=(35+15)(35-15)`

`=50.20`

`=1` `000`

`b)48²-42²+64-52²`

`=48²-42²+8²-52²`

`=(48²-52²)+(8²-42²)`

`=(48+52)(48-52)+(8+42)(8-42)`

`=100.(-4)+50.(-34)`

`=-400-1` `700`

`=-2` `100`

`c)85²-15²`

`=(85+15)(85-15)`

`=100.70`

`=7` `000`

`d)72²+144.16+16²-12²`

`=(72²+144.16+16²)-12²`

`=(72²+2.72.16+16²)-12²`

`=(72+16)²-12²`

`=88²-12²`

`=(88+12)(88-12)`

`=100.76`

`=7` `600`

`e)(43²-11²)/[(36,5)²-(27,5)²]`

`=[(43+11)(43-11)]/[(36,5+27,5)(36,5-27,5)]`

`=(54.32)/(64.9)`

`=(9.3.2.32)/(32.2.9)`

`=3`

`f)73²-13²-10²+20.13`

`=73²-(13²-20.13+10²)`

`=73²-(13²-2.13.10+10²)`

`=73²-(13-10)²`

`=73²-3²`

`=(73+3)(73-3)`

`=76.70`

`=5` `320`

Bài toán 10:

`a)x-3=(3-x)²`

`⇔(x-3)-(3-x)²=0`

`⇔(x-3)-(x-3)²=0`

`⇔(x-3)[1-(x-3)]=0`

`⇔(x-3)(1-x+3)=0`

`⇔(x-3)(4-x)=0`

`(1)x-3=0⇔x=3`

`(2)4-x=0⇔x=4`

Vậy `x∈{3;4}`

`b)x³+3/2x²+3/4x+1/8=1/64`

`⇔x³+3.x². 1/2+3.x. (1/2)^2+(1/2)^3=1/64`

`⇔(x+1/2)^3=(1/4)^3`

`⇔x+1/2=1/4`

`⇔x=1/4-1/2`

`⇔x=1/4-2/4`

`⇔x=-1/4`

Vậy `x=-1/4`

`c)(2x-5)²-(5+2x)²=0`

`⇔[(2x-5)+(5+2x)][(2x-5)-(5+2x)]=0`

`⇔(2x-5+5+2x)(2x-5-5-2x)=0`

`⇔4x.(-10)=0`

`⇔-40x=0`

`⇔x=0`

Vậy `x=0`

`d)` Sửa đề:`27x³-54x²+36=8`

`→27x³-54x²+36x=8`

`27x³-54x²+36x=8`

`⇔27x³-54x²+36x-8=0`

`⇔(3x)³-3.(3x)².2+3.3x.2²-2³=0`

`⇔(3x-2)³=0`

`⇔3x-2=0`

`⇔3x=2`

`⇔x=2/3`

Vậy `x=2/3`

`e)x²-10x=-25`

`⇔x²-10x+25=0`

`⇔x²-2.x.5+5²=0`

`⇔(x-5)²=0`

`⇔x-5=0`

`⇔x=5`

Vậy `x=5`

`f)4x²-4x=-1`

`⇔4x²-4x+1=0`

`⇔(2x)²-2.2x.1+1²=0`

`⇔(2x-1)²=0`

`⇔2x-1=0`

`⇔2x=1`

`⇔x=1/2`

Vậy `x=1/2`