23: ĐKXĐ: x<>5
\(\dfrac{x-1}{x-5}=\dfrac{6}{7}\)
=>7(x-1)=6(x-5)
=>7x-7=6x-30
=>7x-6x=-30+7
=>x=-23(nhận)
24: ĐKXĐ: x<>-1
\(\dfrac{2x-3}{x+1}=\dfrac{4}{7}\)
=>7(2x-3)=4(x+1)
=>14x-21=4x+4
=>14x-4x=4+21
=>10x=25
=>\(x=\dfrac{25}{10}=\dfrac{5}{2}\left(nhận\right)\)
25: \(\dfrac{x-1}{3}=\dfrac{x+3}{5}\)
=>5(x-1)=3(x+3)
=>5x-5=3x+9
=>5x-3x=5+9
=>2x=14
=>x=7
26: \(\dfrac{2x+3}{7}=\dfrac{4x-1}{15}\)
=>15(2x+3)=7(4x-1)
=>30x+45=28x-7
=>30x-28x=-7-45
=>2x=-52
=>x=-26
27: ĐKXĐ: \(x\ne-\dfrac{5}{3}\)
\(\dfrac{2x+1}{3x+5}=\dfrac{3}{7}\)
=>\(7\left(2x+1\right)=3\left(3x+5\right)\)
=>14x+7=9x+15
=>14x-9x=15-7
=>5x=8
=>\(x=\dfrac{8}{5}\left(nhận\right)\)
28: \(\dfrac{2x+3}{24}=\dfrac{3x-1}{32}\)
=>\(\dfrac{4\left(2x+3\right)}{96}=\dfrac{3\left(3x-1\right)}{96}\)
=>9x-3=8x+12
=>9x-8x=12+3
=>x=15
29: ĐKXĐ: \(x\ne-\dfrac{5}{7}\)
\(\dfrac{11x-2}{7x+5}=\dfrac{11}{8}\)
=>\(8\left(11x-2\right)=11\left(7x+5\right)\)
=>88x-16=77x+55
=>88x-77x=55+16
=>11x=71
=>\(x=\dfrac{71}{11}\left(nhận\right)\)
30: \(\dfrac{6x-5}{-7}=\dfrac{5x-3}{-5}\)
=>\(\dfrac{6x-5}{7}=\dfrac{5x-3}{5}\)
=>7(5x-3)=5(6x-5)
=>35x-21=30x-25
=>35x-30x=-25+21
=>5x=-4
=>\(x=-\dfrac{4}{5}\left(nhận\right)\)
31: \(\dfrac{12-7x}{-13}=\dfrac{4-3x}{-5}\)
=>\(\dfrac{7x-12}{13}=\dfrac{3x-4}{5}\)
=>\(13\left(3x-4\right)=5\left(7x-12\right)\)
=>39x-52=35x-60
=>39x-35x=-60+52
=>4x=-8
=>x=-2
giúp mình bài 2.4 thôi ạ , mình cần gấp ạ
