Question

Thu gọn các biểu thức : a) 3.(2x-1) -|x-5| b) |2x+3| + x+2

Answer 1

a: =6x-3-|x-5|

Trường hợp 1: x>=5

A=6x-3-x+5=5x+2

Trường hợp 2: x<5

A=6x-3-(5-x)=6x-3+x-5=7x-8

b: Trường hợp 1: x>=-3/2

A=2x+3+x+2=3x+5

Trường hợp 2: x<-3/2

A=-2x-3+x+2=-x-1

Answer 2

`a)3(2x-1)-|x-5|`

`@TH1: x-5 >= 0<=>x >= 5=>|x-5|=x-5`

   `=>3(2x-1)-(x-5)=6x-3-x+5=5x+2`

`@TH2: x-5 < 0<=>x < 5=>|x-5|=5-x`

   `=>3(2x-1)-(5-x)=6x-3-5+x=7x-8`

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`b)|2x+3|+x+2`

`@TH1:2x+3 >= 0<=>x >= [-3]/2=>|2x+3|=2x+3`

     `=>2x+3+x+2=3x+5`

`@TH2:2x+3 < 0<=>x < [-3]/2 =>|2x+3|=-2x-3`

     `=>-2x-3+x+2=-x-1`