Question

Tìm x biết:
a. x - (3x+1)= 6
b. 4x - 2(x+3) = 6-x
c. lx-3l - 2x= 6 

Answer 1

b)4x - 2x - 6 = 6 - x

2x - 6 = 6- x

6=x-6

Answer 2

a. x-(3x+1)=6

<=> x-3x-1=6.<=> -2x-1=6.<=> -2x=6+1=7.<=> x=7:(-2).<=>x= -3,5.

b. 4x-2(x+3)=6-x

<=> 4x-2x-6=6-x. <=> 4x-2x-6-6+x=0. <=> 3x-12=0. <=>  3x=12. <=> x=4.

c. lx-3l - 2x=6.

* x-3-2x=6. <=> -x-3=6. <=> -x=9. <=> x=-9.

* x-3-2x= -6. <=> -x-3=-6. <=> -x=-3. <=> x=3.

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Answer 3

a)x-(3x+1)=6 <=> x-3x-1=6 <=> x-3x=6+1 <=> -2x=7 <=> x=-3,5

Vậy x=-3,5

b)4x-2(x+3)=6-x <=> 4x-2x-6=6-x <=> 4x-2x+x=6+6 <=> 3x=12 <=> x=4

Vậy x=4

c)lx-3l-2x=6

(+) lx-3l=x-3 khi x-3>=0 <=>x>=3

pt: x-3-2x=6

<=>x-2x=6+3

<=>-x=9

<=>x=-9 (KTMĐK)

(+)lx-3l=-x+3 khi x-3<0 <=> x<3

pt: -x+3-2x=6

<=>-x-2x=6-3

<=>-3x=3

<=>x=-1(TMĐK)

Vậy S={-1}