1. cho \(\frac{a}{b}=\frac{c}{d};\)(b,c,d khac 0)
cmr: \(\frac{a-b}{a+b}=\frac{c-d}{c+d}\); \(\frac{a\cdot b}{c\cdot d}=\frac{\left(a+b\right)^2}{\left(c+d\right)^2}\)
Cho tỉ lệ thúc a/b=c/d .C/minh rang ta có các tlt sau
a)\(\frac{3a+5b}{3a-5b}\)=\(\frac{3c+5d}{3c-5d}\)
b)\(\left(\frac{a+b}{c+d}\right)\) =\(\frac{a^2+b^2}{c^2+d^2}\)
c)\(\frac{a-b}{a+b}\)=\(\frac{c-d}{c+d}\)
d)\(\frac{ab}{cd}\)=\(\left(\frac{a-b}{c-d}\right)^2\)
\(tìmx,y,z:cho\frac{a}{b}=\frac{c}{d}vab+dkhac0.cmr:\frac{a^2+c^2}{b^2+d^2}=\frac{\left(a+c\right)^2}{\left(b+d\right)^2}\)
Cho \(\frac{a}{b}=\frac{c}{d}.CMR\):
b, \(\frac{\left(a+b\right)^2}{a^2+b^2}=\frac{\left(c+d^2\right)}{c^2+d^2}\)
cho tỉ lệ thức sau \(\frac{a}{b}=\frac{c}{d}\):
CMR:
a\(\frac{a^2-b^2}{ab}=\frac{c^2-d^2}{cd}\)
b\(\frac{\left(a+b\right)^2}{a^2+b^2}=\frac{\left(c+d\right)^2}{c^2+d^2}\)
Cho : \(\frac{a}{b}=\frac{c}{d}CMR:\)\(\frac{ab}{cd}=\frac{a^2-b^2}{c^2-d^2}v\text{à}\left(\frac{a+b}{c+d}\right)^2=\frac{a^2+b^2}{c^2+d^2}\)
bài 1: cho tỉ lệ thức \(\frac{a}{b}=\frac{c}{d}\)
a) CMR: (a+2c)(b+d)=(a+c)(b+2d) \(\left(b,d\ne0\right)\)
b) CMR: (a+c)(b-d)=ab-cd
c) CMR: \(\frac{a}{a-b}=\frac{c}{c-d}\left(a,b,c,d>0;a\ne b,c\ne d\right)\)
bài 2: cho \(\frac{a}{b}=\frac{b}{c}=\frac{c}{d}CMR:\left(\frac{a+b+c}{b+c+d}\right)^3=\frac{a}{d}\)
,Cho a/b=c/d CMR .Các tỉ lệ thức sau bằng nhau ( giả thiết các tỉ lệ thức đều có nghĩa )
\(\left(\frac{a+b}{c+d}\right)^2=\frac{a^2+b^2}{c^2+d^2}\)
Còn cách CM nào khác cách này ko \(\frac{a}{b}=\frac{c}{d}\Rightarrow\frac{a}{c}=\frac{b}{d}=\frac{a+b}{c+d}\)
\(\Rightarrow\left(\frac{a+b}{c+d}\right)^2=\frac{a^2}{c^2}=\frac{b^2}{d^2}=\frac{a^2+b^2}{c^2+d^2}\)
\(\Rightarrow\left(\frac{a+b}{c+d}\right)^2=\frac{a^2+b^2}{c^2+d^2}\)
1) Cho \(\frac{a}{b}\)\(=\)\(\frac{c}{d}\)
CMR:
a) \(\left(\frac{a+b}{c+d}\right)^2\)\(=\)\(\frac{a^2+b^2}{c^2+d^2}\)
b) \(\frac{7a^2+5ac}{7a^2+5ac}=\frac{7b^2+5bd}{7b^2+5bd}\)
Sử Dụng Tính Chất Của Dãy Tỉ Số Bằng Nhau
2) Cho \(\frac{a}{2003}=\frac{b}{2004}=\frac{c}{2005}\)
CMR:
\(4\left(a-b\right)\left(b-c\right)=\left(c-d\right)^2\)
3) Cho \(\frac{a}{b}=\frac{c}{d}\)
CMR: \(\frac{2015a-2016b}{2016c+2017d}=\frac{2015c-2016d}{2016a+2017b}\)
