Đáp án:
bai4:
a,3(2x-1)(x+2)-2(3x+2)(x-4)=5
<=> 3( $2x^{2}$+3x-2)-2( $3x^{2}$-12x+2x-8)=5
<=> $6x^{2}$+12x-3x-6-$6x^{2}$ -24x+4x-16=5
<=>-11x=5+22
<=>-11x=27
<=>x=$\frac{-27}{11}$
b,(3x+2)(2x+9)-(x-2)(6x+1)=(x+1)-(x-6)
<=>$6x^{2}$+27x+4x+18- ($6x^{2}$+x-12x-2)=X+1-x+6
<=>$6x^{2}$+31x+18- 6$x^{2}$+11x+2=7
<=>42x+20=7
<=>42x=-13
<=>x=$\frac{-13}{42}$
bai6:
c,(x+1)(x+2)-(x-3)(x+4)=6
<=>$x^{2}$+2x+x+2-($x^{2}$+4x-3x-12)=6
<=>$x^{2}$+3x+2-$x^{2}$-x+12=6
<=>2x+14=6
<=>2x=20
<=>10
d,3(2x-1)(3x-1)-(2x-3)(9x-1)=0
<=>3(6$x^{2}$-5x+1)-($18x^{2}$-29x+3)=0
<=>$18x^{2}$-15x+3-$18x^{2}$+29x-3=0
<=>14x=3-3
<=>14x=0
<=>x=0
vo nghiem
e,(2x-1)(3 - x) + (x - 2)(x + 3) =(1 - x)(x - 2)
<=>6x-$2x^{2}$-3+x+$x^{2}$+3x-2x-6=x-2-$x^{2}$+2x
<=>-$x^{2}$+8x-9=-$x^{2}$+3x-2
<=>8x-3x=-2+9
<=>5x=7
<=>x= $\frac{7}{5}$
Giải thích các bước giải:kh hieu hoi minh nha