Question

Cho a, b, c, d \(\ne\)0. Từ tỉ lệ thức \(\frac{a}{b}=\frac{c}{d}\)hãy suy ra tỉ lệ thức \(\frac{a-b}{a}=\frac{c-d}{c}\)

Làm ơn giúp mình, mình đang cần gấp!

Answer 1

a/b=c/d

=>ad=bc

=>ac-ad=ac-bc

=>a(c-d)=c(a-b)

=>(a-b)/a=(c-d)/c

Answer 2

a/b=c/d=>ad=bc

=>b/a=d/c

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

=>a-b/a=c-d/c

=>đpcm

Answer 3

\(\text{Vì }\frac{a}{b}=\frac{c}{d}\text{ nên :}\frac{a}{c}=\frac{b}{d}\)

\(\text{Mặt khác: }\frac{a}{c}=\frac{b}{d}=\frac{a-b}{c-d}\)

\(\frac{a}{c}=\frac{a-b}{c-d}\Rightarrow\frac{a-b}{a}=\frac{c-d}{c}\)

Answer 4

Ta có: \(\frac{a}{b}-1=\frac{a}{b}-\frac{b}{b}=\frac{a-b}{b}\)(ĐPCM)

\(\frac{c}{d}-1=\frac{c}{d}-\frac{d}{d}=\frac{c-d}{d}\)(ĐPCM)