a)
<=> 2x - 3 + 5x = 4x + 12
<=> 7x - 3 = 4x + 12
<=> 7x - 4x = 12 + 3
<=> 3x = 15
<=> x = 5
b)
<=> 2x - + 5x^2 - 5x = 5x^2
<=> 2x - 5x - 6 = 0
<=> -3x - 6 = 0
<=> -3x = 6
<=> x = -2
c)
<=> 21(4x + 3) - 15(6x - 2)/ 105 = 35(5x + 4) +315/ 105
<=> 84x + 63 - 90x + 30 = 175x + 140 + 315
<=> -6x + 93 = 175x + 455
<=> -6x - 175x = 455 - 93
<=> -181x = 362
<=> x = -2
d)
<=> 5(5x + 2) - 10(8x - 1)/30 = 6(4x + 2) - 150/30
<=> 25x + 10 - 80x + 10 = 24x + 12 -150
<=> -55x + 20 = 24x - 138
<=> -79x = -158
<=> x = 2
e)
<=> x^2 - 4 - (3x - 2x^2 - 6 + 4x) = 0
<=> x^2 - 4 - ( 7x - 2x^2 - 6) = 0
<=> x^2 - 4 - 7x + 2x^2 + 6 = 0
<=> 3x^2 + 2 - 7x = 0
<=> x = - ( -7) cộng trừ căn bậc ( - 7)^2 - 4 nhân 3 nhân 2/ 2 nhân 3
<=> x = 7 công trừ 5/ 6
<=> x= 2, x = 1/3
f)
<=> ( x+ 2) ( x^2 - 3x +5) - (x+2)^2 (x-1) = 0
<=> ( x + 2) [x^2 - 3x +5 - ( x + 2)(x - 1)] = 0
<=> (x + 2) (x^2 - 3x + 5 - x^2 - x + 2) = 0
<=> (x+2) ( -4x + 7) = 0
TH1 : x + 2 = 0
x= -2
TH2 : -4x + 7 =0
x = 7/4
g)
<=> 2x^2 - 2x - 3x + 3 =0
<=> 2x ( x- 1) - 3 ( x-1) = 0
<=> ( x- 1) ( 2x - 3) = 0
TH1 : x - 1= 0
x = 1
TH2 : 2x - 3 = 0
x = 3/2
