Giải thích các bước giải:
`7, 3x^2-14x-5=0`
⇒`3x^2+x-15x-5=0`
⇒`(3x+1)(x-5)=0`
⇒ `x=-1/3` hoặc `x=5`
`8, 2x^2+9x-11=0`
⇒`x(2x+11)-(2x+11)=0`
⇒`(2x+11)(x-1)=0`
⇒`x=-11/2` hoặc `x=1`
`9, (2x-3)^2+(7-x)(2x-3)=0`
⇒`(2x-3)(x+4)=0`
⇒`x=3/2` hoặc `x=-4`
`10, 1+(2x)/(x+4)+27/(2x^2+7x-4)=6/(2x-1)`
⇒`x` ≠ `-4,1/2`
⇒`(2x)/(x+4)+27/(2x^2+7x-4)-6/(2x-1)=-1`
⇒`(2x)/(x+4)+27/((x+4)(2x-1))-6/(2x-1)=-1`
⇒`(2x(2x-1)+27-6(x+4))/((x+4)(2x-1))=-1`
⇒`((2x-1)(2x-3))/((x+4)(2x-1))=-1`
⇒`2x-3=-(x-4)`
⇒`x=-1/3`
`12, (3x-1)/(x-1)-(2x+5)/(3+x)-35/(x^2+x-6)=1`
⇒`x`$\neq$ `1,-3,2`
⇒`(3x-1)/(x-1)-(2x+5)/(3+x)-35/(x^2+x-6)-1=0`
⇒`((3+x)(x-2)(3x-1)-(x-1)(x-2)(2x+5)-35(x-1)-(x-1)(3+x)(x-2))/((x-2)(3+x)(x-2))=0`
⇒`(3x^2-36x+25)/((x-1)(3+x)(x-2))=0`
⇒`3x^2-36x+25=0`
⇒`x=`±$\frac{18±\sqrt{249} }{3}$
`13, 1/(x+2)+2/(2-x)=(2x-3)/(x^2-4)`
⇒`x`$\neq$ `-2,2`
⇒`1/(x+2)+2/(2-x)-(2x-3)/(x^2-4)=0`
⇒`1/(x+2)+2/(2-x)-(2x-3)/((x-2)(x+2))=0`
⇒`(x-2-2(x+2)-(2x-3))/((x-2)(x+2))=0`
⇒`(-3x-3)/((x-2)(x+2))=0`
⇒`-3x-3=0`
⇒`x=-1`
`14, (x+1)/39+(x+2)/38=(x+3)/37+(x+4)/36`
⇒`(x+1)/39+1+(x+2)/38+1=(x+3)/37+1+(x+4)/36+1`
⇒`(x+40)/39+(x+40)/38=(x+40)/37+(x+40)/36`
⇒`(x+40)/39+(x+40)/38-(x+40)/37-(x+40)/36=0`
⇒`(x+40)(1/39+1/38-1/37-1/36)=0`
⇒`x+40=0`
⇒`x=-40`
`15, 5x^2+16x+3=0`
⇒`5x(x+3)+x+3=0`
⇒`(x+3)(5x+1)=0`
⇒`x=-3` hoặc `x=-1/5`
