Question

Answer 1

`a)3x(4x-3)-2x(5-6x)=0`

`<=>12x^2-9x-10x+12x^2=0`

`<=>24x^2-19x=0`

`<=>x(24x-19)=0`

`<=>` \(\left[ \begin{array}{l}x=0\\x=\dfrac{19}{24}\end{array} \right.\) 

`b)5(2x-3)+4x(x-2)+2x(3-2x)=0`

`<=>10x-15+4x^2-8x+6x-4x^2=0`

`<=>8x-15=0`

`<=>8x=15`

`<=>x=15/8`

`c)3x(2-x)+2x(x-1)=5x(x+3)`

`<=>6x-3x^2+2x^2-2x=5x^2+15x`

`<=>6x^2+11x=0`

`<=>x(6x+11)=0`

`<=>` \(\left[ \begin{array}{l}x=0\\x=-\dfrac{11}{6}\end{array} \right.\) 

`d)3x(x+1)-5x(3-x)+6(x^2+2x+3)=0`

`<=>3x^2+3x-15x+5x^2+6x^2+12x+18=0`

`<=>14x^2+18=0`

`<=>14x^2=-18`

`<=>x^2=-9/7` vô lý vì `x^2>=0`