Đáp án+Giải thích các bước giải:

1) $x^2-7x=0$
<=>$x(x-7)=0$
<=>\(\left[ \begin{array}{l}x=0\\x=7\end{array} \right.\)

=> KL: $phương$ $trình$ $có$ $tập$ $nghiệm$$S$={$0;7$}
2)$-3x^2+5x=0$
<=>$-x(3x-5)=0$

<=>\(\left[ \begin{array}{l}x=0\\x=5/3\end{array} \right.\)

=> KL:…
3)$x^2+3x-2x-6=0$
<=>$x^2-x-6=0$
<=>$x^2+x-6x-6=0$
<=>$x(x+1)-6(x+1)=0$
<=>$(x-6)(x+1)=0$

<=>\(\left[ \begin{array}{l}x=6\\x=-1\end{array} \right.\)

=> KL:…
4) $x^2+6x-x-6=0$
<=>$x(x+6)-(x+6)=0$
<=>$(x-1)(x+6)=0$
<=>\(\left[ \begin{array}{l}x=1\\x=-6\end{array} \right.\)

=> KL…
5) $x^2+2x-3x-6=0$
<=>$x(x+2)-3(x+2)=0$
<=>$(x-3)(x+2)=0$
<=>\(\left[ \begin{array}{l}x=3\\x=-2\end{array} \right.\)

=> KL:…
6) $x^2-4x+5x=0$
<=>$x^2+x=0$
<=>$x(x+1)=0$
<=>\(\left[ \begin{array}{l}x=0\\x=-1\end{array} \right.\) 

=> KL:…

7)$x^2+4x-5x-20=0$
<=>$x(x+4)-5(x+4)=0$
<=>$(x-5)(x+4)=0$
<=>\(\left[ \begin{array}{l}x=5\\x=-4\end{array} \right.\) 

=> KL:…
8) $x^2-10x+2x-20=0$
<=>$x(x-10)+2(x-10)=0$
<=>$(x+2)(x-10)=0$
<=>\(\left[ \begin{array}{l}x=-2\\x=10\end{array} \right.\) 

=> KL:…
9) $x^2+10x-2x-20=0$
<=>$x(x+10)-2(x+10)=0$
<=>$(x-2)(x+10)=0$
<=>\(\left[ \begin{array}{l}x=2\\x=-10\end{array} \right.\) 

=> KL:…
10) $x^2-20x+x-20=0$
<=>$x(x-20)+(x-20)=0$
<=>$(x+1)(x-20)=0$
<=>\(\left[ \begin{array}{l}x=-1\\x=20\end{array} \right.\) 

=> KL:…
11) $x^2+20x-x-20=0$
<=>$x(x+20)-(x+20)=0$
<=>$(x-1)(x+20)=0$
<=>\(\left[ \begin{array}{l}x=1\\x=-20\end{array} \right.\) 

=> KL:…
12) $x^2+12x+2x+24=0$
<=>$x(x+12)+2(x+12)=0$
<=>$(x+2)(x+12)=0$
<=>\(\left[ \begin{array}{l}x=-2\\x=-12\end{array} \right.\) 

=> KL:…
13) $x^2-12x-2x+24=0$
<=>$x(x-12)-2(x-12)=0$
<=>$(x-2)(x-12)=0$
<=>\(\left[ \begin{array}{l}x=2\\x=12\end{array} \right.\) 

=> KL:…
14) $x^2+6x+4x+24=0$
<=>$x(x+6)+4(x+6)=0$
<=>$(x+4)(x+6)=0$
<=>\(\left[ \begin{array}{l}x=-4\\x=-6\end{array} \right.\) 

=> KL:…
15) $x^2-6x-4x+24=0$
<=>$x(x-6)-4(x-6)=0$
<=>$(x-4)(x-6)=0$
<=>\(\left[ \begin{array}{l}x=-4\\x=-6\end{array} \right.\) 

=> KL:…
16) $x^2+8x+3x+24=0$
<=>$x(x+8)+3(x+8)=0$
<=>$(x+3)(x+8)=0$
<=>\(\left[ \begin{array}{l}x=-3\\x=-8\end{array} \right.\) 

=> KL:…
17) $x^2-8x-3x+24=0$
<=>$x(x-8)-3(x-8)=0$
<=>$(x-3)(x-8)=0$
<=>\(\left[ \begin{array}{l}x=3\\x=8\end{array} \right.\) 

=> KL:…
18) $x^2-8x+3x-24=0$
<=>$x(x-8)+3(x-8)=0$
<=>$(x+3)(x-8)=0$
<=>\(\left[ \begin{array}{l}x=-3\\x=8\end{array} \right.\) 

=> KL:…
19) $x^2-8x+3x-24=0$
<=>$x(x-8)+3(x-8)=0$
<=>$(x+3)(x-8)=0$
<=>\(\left[ \begin{array}{l}x=-3\\x=8\end{array} \right.\) 

=> KL:…
20) $x^2-5x-24=0$
<=>$x^2+3x-8x-24=0$
<=>$x(x+3)-8(x+3)=0$
<=>$(x-8)(x+3)=0$
<=>\(\left[ \begin{array}{l}x=8\\x=-3\end{array} \right.\) 

=> KL:…