Đáp án:
Giải thích các bước giải:
7, 3x(x+5) - 2x - 10 = 0
⇒$3x^{2}$ +15x -2x -10 = 0
⇒$3x^{2}$ +13x -10= 0
⇒x(3x+13) = 10
⇒\(\left[ \begin{array}{l}x=10\\3x+13=10\end{array} \right.\)
⇒$\left \{ {{x=10} \atop {x=\frac{-13}{3}}} \right.$
8, x-3+3x(x-3) = 0
⇒x-3+3x²-9x = 0
⇒3x²-8x =3
⇒x(3x-8)= 3
⇒\(\left[ \begin{array}{l}x=3\\3x-8=3\end{array} \right.\)
⇒\(\left[ \begin{array}{l}x=3\\x=11/3\end{array} \right.\)
9. 3x-2+2x(3x-2) = 0
⇒3x-2 +6x²-4x = 0
⇒6x²-x-2 = 0
⇒6x²-x = 2
⇒x(6x-1) = 2
⇒\(\left[ \begin{array}{l}x=2\\6x-1=2\end{array} \right.\)
⇒\(\left[ \begin{array}{l}x=2\\x=1/2\end{array} \right.\)
12. x(x+2)+2=-x
⇒x² +2x +2 +x = 0
⇒x² + 3x = -2
⇒x(x+3) = -2
⇒\(\left[ \begin{array}{l}x=-2\\x+3=-2\end{array} \right.\)
⇒\(\left[ \begin{array}{l}x=-2\\x=-5\end{array} \right.\)
13. 4+2x(2x+4)= -x
⇒4+4x²+8x +x = 0
⇒4x²+9x =-4
⇒x(4x+9)= -4
⇒\(\left[ \begin{array}{l}x=-4\\4x+9=-4\end{array} \right.\)
⇒\(\left[ \begin{array}{l}x=-4\\x=13/4\end{array} \right.\)
14.3x(x-3)=-x+3
⇒3x²-9x+x-3 = 0
⇒3x²-8x = 3
⇒x(3x-8) = 3
⇒\(\left[ \begin{array}{l}x=3\\3x-8=3\end{array} \right.\)
⇒\(\left[ \begin{array}{l}x=3\\x=11/3\end{array} \right.\)
Mình bận nên ko làm hết được . Sorry.
Wish luck for u .ω.
