Răspuns :
(3-x)/x=(3x+1)/(7-x)
(3-x)(7-x)=x(3x+1)
21-3x-7x+x²=3x²+3x
x²-3x²-10x-3x+21=0
-2x²-13x+21=0 inmultim -1
2x²+13x-21=0
Δ=169+168=337
x1=(-13+√337)/4
x2=(-13-√337)/4
(3-x)(7-x)=x(3x+1)
21-3x-7x+x²=3x²+3x
x²-3x²-10x-3x+21=0
-2x²-13x+21=0 inmultim -1
2x²+13x-21=0
Δ=169+168=337
x1=(-13+√337)/4
x2=(-13-√337)/4
[tex]\dfrac{3-x}{x}=\dfrac{3x+1}{7-x}[/tex]
[tex](3-x)(7-x)=x(3x+1)\Rightarrow 21-3x-7x+x^2=3x^2+x\Rightarrow[/tex]
[tex]2x^2+11x-21=0[/tex]
[tex]\Delta=289\Rightarrow \sqrt{\Delta}=17\Rightarrow x_1=\dfrac32;\ \ x_2=-7[/tex]
[tex](3-x)(7-x)=x(3x+1)\Rightarrow 21-3x-7x+x^2=3x^2+x\Rightarrow[/tex]
[tex]2x^2+11x-21=0[/tex]
[tex]\Delta=289\Rightarrow \sqrt{\Delta}=17\Rightarrow x_1=\dfrac32;\ \ x_2=-7[/tex]
