Question

tim x

a,\(\frac{7}{x+1}\)=\(\frac{5}{x-1}\)

b, \(\frac{2.x}{9}\)=\(\frac{-8}{-x}\)

c,\(\frac{x-3}{36}\)=\(\frac{-4}{3-x}\)

 

Answer 1

a) 7(x-1)=5(x+1)

=>7x-7=5x+5

7x-5x=7+5

2x=12

=>x=6

b) =>2x.(-x) =9.-8

-2x²=-72

x²=36

=> x=6 hoặc -6

c) (x-3)(3-x) = 36.-4

=>3x-x²-3.3+x²=-144

x(3-x+x)-9=-144

3x=-135

x=-45

Answer 2

giai cu the ho minh nha cac ban

Answer 3

a/ \(\frac{7}{x+1}=\frac{5}{x-1}\)  =>  7 (x - 1) = 5 (x + 1)

=> 7x - 7 = 5x + 5

=> 7x - 5x = 5 + 7

=> 2x = 12

=> x = 6

b/ \(\frac{2x}{9}=\frac{-8}{-x}\Rightarrow\frac{2x}{9}=\frac{8}{x}\) => 2xx = 8 . 9

=> 2x² = 72

=> x² = 36

=> x = ±6

c/ \(\frac{x-3}{36}=\frac{-4}{3-x}\Rightarrow\frac{x-3}{36}=\frac{4}{x-3}\)  => (x - 3) (x - 3) = 36 . 4 

=> (x - 3)² = 144

=> x - 3 = ±12

TH1 : x - 3 = 12 => x = 15

TH2 : x - 3 = -12 => x = -9