Bài 1: a) 4(18-5x) -12(3x-7) = 15(2x-16)- 6(x+14)
72 -20x-36x+84 =30x-240 -6x-84
-80x = -480
x = 6
b) 5x-3[4x-2(4x -15x +6)]=182
5x-3(4x-8x+30x-12) =182
5x-12x+24x-90x+36 =182
-73x = 146
x = -2
c) -3x^2 +15x+5x-5 +3x^2 =4-x
21x =9
x = 3/7
d)x^2 +5x +6 -x^2 -3x+10 =6
2x = -10
x = -5
e)6x^2 +27x+4x+18 - 6x^2 -x-12x-1=x+1-x+6
18x = -10
x= -5/9
f) x^3 -27 +5x-x^3 =6x
x = -27
g) 3(6x^2 -2x -3x+1) -2(9x^2-x -27x+3) =0
18x^2 -15x+3 -18x^2 +54x-6=0
39x = 3
x = 1/13
h) [(x+1)(x-3)].[(x+2)(x-4)] = (x^2 -2x-3)^2 -5x^2
(x^2 -2x-3).(x^2-2x-8) -(x^2-2x-3)^2 +5x^2 =0
(x^2 -2x-3).(x^2-2x-8-x^2 +2x+3) +5x^2 =0
-5(x^2 -2x-3) + 5x^2 =0
-5(x^2 -2x-3- x^2) =0
-5(-2x-3) =0
-2x-3 =0
-2x = 3
x= -3/2
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