tìm x biết: 1) a) (x+1)(x+3)-x(x-1)=8 b) 9x^2= 1-(3x+1)(2x-9) 01/12/2021 Bởi Autumn tìm x biết: 1) a) (x+1)(x+3)-x(x-1)=8 b) 9x^2= 1-(3x+1)(2x-9)
a)(x+1)(x+3)-x(x-1)=8 x² +4x+3- x²+x=8 5x=5 x=1 Vậy x=1 b) 9x²= 1-(3x+1)(2x-9) 9x²=1- 6x² +27x -2x +9 15x²-25x-10=0 x²-$\frac{5}{3}$x -$\frac{2}{3}$ =0 x² -2x +$\frac{1}{3}$x -$\frac{2}{3}$=0 x(x-2)+$\frac{1}{3}$(x-2)=0 (x+$\frac{1}{3}$).(x-2)=0 \(\left[ \begin{array}{l}x+\frac{1}{3}\\x-2=0\end{array} \right.\) \(\left[ \begin{array}{l}x=-\frac{1}{3}\\x=2\end{array} \right.\) Vậy \(\left[ \begin{array}{l}x=-\frac{1}{3}\\x=2\end{array} \right.\) Bình luận
Đáp án: Bài 1: giải các pt sau: a,(x-1)^2-(x+1)^2=2(x+3) (2x-1)^2-(2x+1)^2=4(x-3) (2x+3)^2-(2x+3).(2x-4)=-(x-2)^2 b,9x^12-(x+1)^3=3x-3 (3x-2).(9x^2+6x+4)-(3x+1).(9x^2-3x+1)=(2x+1).(2x-1)-4x(x-3) Giải thích các bước giải: Bình luận
a)(x+1)(x+3)-x(x-1)=8
x² +4x+3- x²+x=8
5x=5
x=1
Vậy x=1
b) 9x²= 1-(3x+1)(2x-9)
9x²=1- 6x² +27x -2x +9
15x²-25x-10=0
x²-$\frac{5}{3}$x -$\frac{2}{3}$ =0
x² -2x +$\frac{1}{3}$x -$\frac{2}{3}$=0
x(x-2)+$\frac{1}{3}$(x-2)=0
(x+$\frac{1}{3}$).(x-2)=0
\(\left[ \begin{array}{l}x+\frac{1}{3}\\x-2=0\end{array} \right.\)
\(\left[ \begin{array}{l}x=-\frac{1}{3}\\x=2\end{array} \right.\)
Vậy \(\left[ \begin{array}{l}x=-\frac{1}{3}\\x=2\end{array} \right.\)
Đáp án:
Bài 1: giải các pt sau:
a,(x-1)^2-(x+1)^2=2(x+3)
(2x-1)^2-(2x+1)^2=4(x-3)
(2x+3)^2-(2x+3).(2x-4)=-(x-2)^2
b,9x^12-(x+1)^3=3x-3
(3x-2).(9x^2+6x+4)-(3x+1).(9x^2-3x+1)=(2x+1).(2x-1)-4x(x-3)
Giải thích các bước giải: