\(\frac{a}{b}=\frac{c}{d}\Rightarrow a.d=b.c\Rightarrow\frac{a}{c}=\frac{b}{d}\)
\(\frac{a}{c}=\frac{b}{d}\Rightarrow\frac{5a}{5c}=\frac{5b}{5d}=\frac{5a+5b}{5c+5d}=\frac{5a-5b}{5c-5d}\)
\(\Rightarrow\frac{5a+5b}{5c+5d}=\frac{5a-5b}{5c-5d}\)
\(\frac{a}{b}=\frac{c}{d}\Rightarrow a.d=b.c\Rightarrow\frac{a}{c}=\frac{b}{d}\)
\(\frac{a}{c}=\frac{b}{d}\Rightarrow\frac{5a}{5c}=\frac{5b}{5d}=\frac{5a+5b}{5c+5d}=\frac{5a-5b}{5c-5d}\)
\(\Rightarrow\frac{5a+5b}{5c+5d}=\frac{5a-5b}{5c-5d}\)
Cho tỉ lệ thức: \(\dfrac{a}{b}=\dfrac{c}{d}\left(a,b,c,d\ne0\right)\)
Chứng minh:
1) \(\dfrac{a+b}{b}=\dfrac{c+d}{d}\)
2) \(\dfrac{5a+3b}{5a-3b}=\dfrac{5c+3d}{5c-3d}\)
Cho\(\dfrac{a}{b}\)=\(\dfrac{c}{d}\). Chứng minh:
a,\(\dfrac{ab}{cd}\)=\(\dfrac{a^2-b^2}{c^2-d^2}\)
b,\(\dfrac{5a+3b}{5a-3b}\)=\(\dfrac{5c+3d}{5c-3d}\)
c,\(\dfrac{7a^2+3ab}{11a^2-8b^2}\)=\(\dfrac{7c^2+3cd}{11c^2-8d^2}\)
. Help Me ! Please :)) Mik đang gấp lắm nhé nên nếu các bạn biết thì giải giúp mik nhé :3 Cảm ơn nhiều nhiều lắm nek ~~~ Bạn nào làm đúng mik sẽ tik nhé =))
Đề bài: Cho a/b = c/d . C/minh rằng
a) 5a-3b/5a+3b = 5c-3d/5c+3d
b) 5a+11b/6a-5b = 5c + 11d/6c-5d
c) 2a^2 - 3b^2/2c^2 - 3d^2 = ab/cd
Cho \(\frac{a}{b}=\frac{c}{d}\)
Chứng minh rằng :\(\frac{5a+b}{5c-d}=\frac{5a-b}{5c+d}\)
Cho tỉ lệ thức \(\frac{a}{b}=\frac{c}{d}\). C/minh \(\frac{2a+3b}{2a-3b}=\frac{2c+3d}{2c-3d}\)
Cho a, b, c, d là các số thực dương. Chứng minh :
\(\frac{a}{b+2c+3d}+\frac{b}{c+2d+3a}+\frac{c}{d+2a+3b}+\frac{d}{a+2b+3c}\ge\frac{2}{3}\)
1.Cho \(\frac{a}{b}\)= \(\frac{c}{d}\)chứng minh :
a. \(\frac{a+c}{b+d}\)=\(\frac{a-c}{b-d}\)
b. \(\frac{2a+3b}{2a-3b}\)=\(\frac{2c+3d}{3c-3d}\)
2. tìm x, biết :
a. \(\frac{-2,6}{x}\)=\(\frac{-12}{42}\)
b. \(\frac{x^2}{6}\)= \(\frac{24}{25}\)
Bài 1:Cho 3 số dương a, b, c thoả mãn a + b + c\(\le\)2018. Chứng minh rằng
\(\frac{5a^3-b^3}{ab+3a^2}+\frac{5b^3-c^3}{bc+3b^2}+\frac{5c^3-a^3}{ca+3c^2}\le2018\)
Cho a,b,c dương thỏa mãn abc= 1.CMR:
\(\frac{1}{b\left(5a+b\right)}+\frac{1}{c\left(5b+c\right)}+\frac{1}{a\left(5c+a\right)}\ge\frac{1}{2}\)