Question

cm : a/b = c/d 
=)) a/a+b= c/c+d

Answer 1

Đặt \(\frac{a}{b}=\frac{c}{d}=k\Rightarrow a=bk;c=dk\)

Ta có: \(\frac{a}{a+b}=\frac{bk}{bk+b}=\frac{bk}{b\left(k+1\right)}=\frac{k}{k+1}^{\left(1\right)}\)

Lại có: \(\frac{c}{c+d}=\frac{dk}{dk+d}=\frac{dk}{d\left(k+1\right)}=\frac{k}{k+1}^{\left(2\right)}\)

Từ ⁽¹⁾ và ⁽²⁾ => \(\frac{a}{a+b}=\frac{c}{c+d}\left(dpcm\right)\)

Answer 2

bố thí, cả tối kiếm đc 4 li-ke,, ít quá