1: \(\Leftrightarrow3x^2-6x-x-3x^2=14\)
=>-7x=14
hay x=-2
2: \(\Leftrightarrow2x^2+6x-3x^2-3=x+1-x^2+2x\)
\(\Leftrightarrow-x^2+6x-3=-x^2+3x+1\)
=>6x-3=3x+1
=>3x=4
hay x=4/3
3: \(\Leftrightarrow-x^2+2x-2x^2+6x-3=-3x^2+6x+8x-20\)
\(\Leftrightarrow-3x^2+8x-3=-3x^2+14x-20\)
=>14x-20=8x-3
=>6x=17
hay x=17/6
1) 3x(x-2) - x(1 + 3x) = 14
<=> 3x2 - 6x - x - 3x2 = 14
<=> -7x = 14
<=> x = -2
2 ) 2x(x+3) - 3(x2 + 1 ) = x+1 - x(x-2)
<=> 2x2 + 6x - 3x2 - 3 = x+1 - x2 + 2x
<=> -x2 + 6x - 3 = -x2 + 3x + 1
<=> -x2 + 6x + x2 + 3x = 1 + 3
<=> 9x = 4
<=> x = \(\dfrac{4}{9}\)
3) x(-x+2) - 2x(x-3) - 3 = -3(x2 - 2x )+ 4(2x - 5)
<=> -x2 + 2x - 2x2 + 6x - 3 = -3x2 + 6x + 8x - 20
<=> -3x2 + 8x -3 = -3x2 + 14x - 20
<=> -3x2 + 8x + 3x2 + 14x = -20 + 3
<=> 22x = -17
<=> x = \(-\dfrac{17}{22}\)
