Toán 3x-1/x-1 – 2x+5/X+3 = X^ 2+2X-7/(X-1)(X+3) 20/11/2021 By Daisy 3x-1/x-1 – 2x+5/X+3 = X^ 2+2X-7/(X-1)(X+3)
$\dfrac{3x-1}{x-1}$ – $\dfrac{ 2x+5}{x+3}$ = $\dfrac{ x^ 2+2x-7}{(x-1)(x+3)}$ <=> $\dfrac{(3x-1)(x+3)}{(x-1)(x+3)}$ – $\dfrac{ (2x+5)(x-1)}{(x-1)(x+3)}$ = $\dfrac{ x^ 2+2x-7}{(x-1)(x+3)}$ <=> $\dfrac{3x^2+8x-3}{(x-1)(x+3)}$ – $\dfrac{ 2x^2+3x-5}{(x-1)(x+3)}$ = $\dfrac{ x^ 2+2x-7}{(x-1)(x+3)}$ $=> 3x^2+8x-3 – 2x^2-3x+5 = x^ 2+2x-7$$=> 3x-3 +5 =-7$$=> 3x =-7+3-5$$=> 3x =-9$$<=> x = -3$Thay lại vào không thoả mãn vì khiến mẫu =0=> vô nghiệm Trả lời
$\dfrac{3x-1}{x-1}$ – $\dfrac{ 2x+5}{x+3}$ = $\dfrac{ x^ 2+2x-7}{(x-1)(x+3)}$
<=> $\dfrac{(3x-1)(x+3)}{(x-1)(x+3)}$ – $\dfrac{ (2x+5)(x-1)}{(x-1)(x+3)}$ = $\dfrac{ x^ 2+2x-7}{(x-1)(x+3)}$
<=> $\dfrac{3x^2+8x-3}{(x-1)(x+3)}$ – $\dfrac{ 2x^2+3x-5}{(x-1)(x+3)}$ = $\dfrac{ x^ 2+2x-7}{(x-1)(x+3)}$
$=> 3x^2+8x-3 – 2x^2-3x+5 = x^ 2+2x-7$
$=> 3x-3 +5 =-7$
$=> 3x =-7+3-5$
$=> 3x =-9$
$<=> x = -3$
Thay lại vào không thoả mãn vì khiến mẫu =0
=> vô nghiệm