cho a/b=c/d. CMR (2b-9)/a=(2d-c)/c
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Cho a/b=c/d CMR a/a+2b=c/c+2d
Đặt \(\dfrac{a}{c}=\dfrac{b}{d}=k\)
\(\Leftrightarrow\left\{{}\begin{matrix}a=ck\\b=dk\end{matrix}\right.\)
\(\dfrac{a}{a+2b}=\dfrac{ck}{ck+2dk}=\dfrac{ck}{k\left(c+2d\right)}=\dfrac{c}{c+2d}\)
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Cho \(\frac{a+2c}{b+2d}=\frac{2a+c}{2b+d}\) .
CMR : \(\frac{a}{b}=\frac{a+c}{b+d};\frac{2a-c}{2b-d}=\frac{a-2c}{b-2d};\frac{a+2b}{a-b}=\frac{c+2d}{c-d}\)
\(\frac{a+2b}{a-2b}=\frac{c+2d}{c-2d}CMR\frac{a}{b}=\frac{c}{d}\)
cho a/b= c/d (b,c,d khac 0; c-2d khac 0) CMR :(a-2b)^4/(c-2d)^4=a^4+2017b^4/c^4+2017d^4
Cho a,b,c,d >0, a + b + c + d=4.cmr: a/(1 + b^2c) + b/(1 + c^2d) + c/(1 + d^2a) + d/(1 + a^2b) >=2
cho a/b=c/d (gt các tỉ số đều có nghĩa)
CMR
a-2b/b=c-2d/d
ta có:
\(\dfrac{a-2b}{b}=\dfrac{a}{b}-\dfrac{2b}{b}=\dfrac{a}{b}-2\\ \dfrac{c-2d}{d}=\dfrac{c}{d}-\dfrac{2d}{d}=\dfrac{c}{d}-2\)
mà \(\dfrac{c}{d}=\dfrac{a}{b}\\ \)
nên: \(\dfrac{a-2b}{b}=\dfrac{c-2d}{d}\)
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cho a/b=c/d. CMR:
a,5a-3b/3a+2b=5c-3d/3c+2d
b,2a+7b/a-2b=2c+d/c-2d
c,ac/bd=(ac)mũ 2/(bd)mũ 2
d,2a mũ 2+3c mũ 2/3b mũ 2+3d mũ 2=5a mũ 2-2c mũ 2/2b mũ 2- 2d mũ 2
Cho a, b, c, d > 0. CMR \(\frac{a^4}{a^3+2b^3}+\frac{b^4}{a^3+2b^3}+\frac{c^4}{c^3+2d^3}+\frac{d^4}{d^3+2a^3}\ge\frac{a+b+c+d}{3}\)
Cho a/b = c/d. CMR a+2b/a = c+2d/c
Có ai biết thì trả lời giúp mình với, tại mình cần gấp á.
Đặt a/b=c/d=k
=>a=bk; c=dk
\(\dfrac{a+2b}{a}=\dfrac{bk+2b}{bk}=\dfrac{k+2}{k}\)
\(\dfrac{c+2d}{c}=\dfrac{dk+2d}{dk}=\dfrac{k+2}{k}\)
=>\(\dfrac{a+2b}{a}=\dfrac{c+2d}{c}\)
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