Toán Lớp 8: 1) x mũ 2 – 7x = 0
2) – 3x mũ 2 + 5x = 0
3) x mũ 2 + 3x _ 2x _ 6 = 0
4) x mũ 2 + 6x – x – 6 = 0
5) x mũ 2 + 2x – 3x – 6 = 0
6) x mũ 2 – 4x + 5x = 0
7) x mũ 2 + 4x – 5x – 20 = 0
8) x mũ 2 – 10x + 2x – 20 = 0
9) x mũ 2 + 10x – 2x – 20 = 0
10 ) x mũ 2 – 20x + x – 20 = 0
11) x mũ 2 + 20x – x – 20 = 0
12) x mũ 2 + 12x + 2x + 24 = 0
13) x mũ 2 – 12x – 2x + 24 = 0
14) x mũ 2 + 6x + 4x + 24 = 0
15) x mũ 2 – 6x – 4x + 24 = 0
16) x mũ 2 + 8x + 3x + 24 = 0
17) x mũ 2 – 8x – 3x + 24 = 0
18) x mũ 2 + 8x – 3x – 24 = 0
19) x mũ 2 – 8x + 3x – 24 = 0
20) x mũ 2 – 5x – 24 = 0
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<=>$x(x-7)=0$
<=>\(\left[ \begin{array}{l}x=0\\x=7\end{array} \right.\)
2)$-3x^2+5x=0$
<=>$-x(3x-5)=0$
3)$x^2+3x-2x-6=0$
<=>$x^2-x-6=0$
<=>$x^2+x-6x-6=0$
<=>$x(x+1)-6(x+1)=0$
<=>$(x-6)(x+1)=0$
4) $x^2+6x-x-6=0$
<=>$x(x+6)-(x+6)=0$
<=>$(x-1)(x+6)=0$
<=>\(\left[ \begin{array}{l}x=1\\x=-6\end{array} \right.\)
5) $x^2+2x-3x-6=0$
<=>$x(x+2)-3(x+2)=0$
<=>$(x-3)(x+2)=0$
<=>\(\left[ \begin{array}{l}x=3\\x=-2\end{array} \right.\)
6) $x^2-4x+5x=0$
<=>$x^2+x=0$
<=>$x(x+1)=0$
<=>\(\left[ \begin{array}{l}x=0\\x=-1\end{array} \right.\)
<=>$x(x+4)-5(x+4)=0$
<=>$(x-5)(x+4)=0$
<=>\(\left[ \begin{array}{l}x=5\\x=-4\end{array} \right.\)
8) $x^2-10x+2x-20=0$
<=>$x(x-10)+2(x-10)=0$
<=>$(x+2)(x-10)=0$
<=>\(\left[ \begin{array}{l}x=-2\\x=10\end{array} \right.\)
9) $x^2+10x-2x-20=0$
<=>$x(x+10)-2(x+10)=0$
<=>$(x-2)(x+10)=0$
<=>\(\left[ \begin{array}{l}x=2\\x=-10\end{array} \right.\)
10) $x^2-20x+x-20=0$
<=>$x(x-20)+(x-20)=0$
<=>$(x+1)(x-20)=0$
<=>\(\left[ \begin{array}{l}x=-1\\x=20\end{array} \right.\)
11) $x^2+20x-x-20=0$
<=>$x(x+20)-(x+20)=0$
<=>$(x-1)(x+20)=0$
<=>\(\left[ \begin{array}{l}x=1\\x=-20\end{array} \right.\)
12) $x^2+12x+2x+24=0$
<=>$x(x+12)+2(x+12)=0$
<=>$(x+2)(x+12)=0$
<=>\(\left[ \begin{array}{l}x=-2\\x=-12\end{array} \right.\)
13) $x^2-12x-2x+24=0$
<=>$x(x-12)-2(x-12)=0$
<=>$(x-2)(x-12)=0$
<=>\(\left[ \begin{array}{l}x=2\\x=12\end{array} \right.\)
14) $x^2+6x+4x+24=0$
<=>$x(x+6)+4(x+6)=0$
<=>$(x+4)(x+6)=0$
<=>\(\left[ \begin{array}{l}x=-4\\x=-6\end{array} \right.\)
15) $x^2-6x-4x+24=0$
<=>$x(x-6)-4(x-6)=0$
<=>$(x-4)(x-6)=0$
<=>\(\left[ \begin{array}{l}x=-4\\x=-6\end{array} \right.\)
16) $x^2+8x+3x+24=0$
<=>$x(x+8)+3(x+8)=0$
<=>$(x+3)(x+8)=0$
<=>\(\left[ \begin{array}{l}x=-3\\x=-8\end{array} \right.\)
17) $x^2-8x-3x+24=0$
<=>$x(x-8)-3(x-8)=0$
<=>$(x-3)(x-8)=0$
<=>\(\left[ \begin{array}{l}x=3\\x=8\end{array} \right.\)
18) $x^2-8x+3x-24=0$
<=>$x(x-8)+3(x-8)=0$
<=>$(x+3)(x-8)=0$
<=>\(\left[ \begin{array}{l}x=-3\\x=8\end{array} \right.\)
19) $x^2-8x+3x-24=0$
<=>$x(x-8)+3(x-8)=0$
<=>$(x+3)(x-8)=0$
<=>\(\left[ \begin{array}{l}x=-3\\x=8\end{array} \right.\)
20) $x^2-5x-24=0$
<=>$x^2+3x-8x-24=0$
<=>$x(x+3)-8(x+3)=0$
<=>$(x-8)(x+3)=0$
<=>\(\left[ \begin{array}{l}x=8\\x=-3\end{array} \right.\)