Question

[Tạ Hoàng Thái]

cho tỉ lệ thức a/b=c/d  a,b,c,d khác 0 cm 

1) a+b/b=c+d/d

2) 5a+3b/5a-3b=5c+3d/5c-3d

Answer 1

[Minh Bui Tuan Minh]

1) Vì a/b = c/d

=> a/b + 1 = c/d + 1

=> a + b/b = c + d/d (đpcm)

2) Vì a/b = c/d

=> a/c = b/d

=> 5a/5c = 3b/3d = 5a + 3b/5c + 3d = 5a - 3b/5c - 3d ( theo tc DTSBN )

=> 5a + 3b/5a - 3b = 5c + 3d/5c - 3d

Answer 2

[Linh nguyen phan khanh]

1,a/b=c/d

=>\(\frac{a}{b}+1=\frac{c}{d}+1\)

=>\(\frac{a+b}{b}=\frac{c+d}{d}\)