Tìm x,biết a) 3( x + 1) + 4( x-2 ) = 7 b) 2( 3x -2 ) – 5 ( x+1) =10 c) 2x ( x+1 ) -2( x + 3 ) = 5 d) 3x ( x-2 )+ x ( 5 – 3x )= 10

$\text{Đáp án+Giải thích các bước giải:}$

$\text{a) 3(x+1)+4(x-2)=7}$

$\text{⇔ 3x+3+4x-8=7}$

$\text{⇔ 7x-5=7}$

$\text{⇔ 7x=12}$

$\text{⇔ x=$\frac{12}{7}$}$

$\text{b) 6x-4-5x-5=10}$

$\text{⇔ x-9=10}$

$\text{⇔ x=19}$

$\text{c) 2x²+2x-2x-6=5}$

$\text{⇔ 2x²=11}$

$\text{⇔ x²=$\frac{11}{2}$}$ 

$\text{⇔ x=±√$\frac{11}{2}$}$

$\text{d) 3x²-6x+5x-3x²=10}$

$\text{⇔ -x=10}$

$\text{⇔ x=-10}$