cho \(\dfrac{2a+13b}{3a-7b}=\dfrac{2c+13d}{3c-7d}\) CMR \(\dfrac{a+b}{b}=\dfrac{c+d}{d}\)
\(\dfrac{2a+13b}{3a-7b}\)=\(\dfrac{2c+13d}{3c-7d}\)
CMR:\(\dfrac{a}{b}=\dfrac{c}{d}\)
mn giải giúp cốm
Ta có: \(\dfrac{2a+13b}{3a-7b}=\dfrac{2c+13d}{3c-7d}\)
\(\Leftrightarrow\dfrac{2a+13b}{2c+13d}=\dfrac{3a-7b}{3c-7d}\)
\(\Leftrightarrow\dfrac{a}{c}+\dfrac{b}{d}=\dfrac{a}{c}-\dfrac{b}{d}\)
\(\Leftrightarrow\dfrac{a}{c}=\dfrac{b}{d}\)
hay \(\dfrac{a}{b}=\dfrac{c}{d}\)
Cho \(\dfrac{2a+13b}{3a-7b}=\dfrac{2c+13d}{3c-7d}.\) CMR : \(\dfrac{a}{b}=\dfrac{c}{d}\)
Giúp mk vs mai mk phải nộp rồi
\(\dfrac{2a+13b}{3a-7b}=\dfrac{2c+13d}{3c-7d}\)
\(\Leftrightarrow\left(2a+13b\right)\left(3c-7d\right)=\left(2c+13d\right)\left(3a-7b\right)\)
\(\Leftrightarrow6ac-14ad+39bc-91bd=6ac-14bc+39ad-91bd\)
\(\Leftrightarrow-53ad=-53bc\)
=>ad=bc
hay a/b=c/d
Cho tỉ lệ thức \(\dfrac{2a+13b}{3a-7b}=\dfrac{2x+13d}{3c-7d}\)
Chứng minh rằng \(\dfrac{a}{b}=\dfrac{c}{d}\)
\(\dfrac{2a+13b}{3a-7b}=\dfrac{2c+13d}{3c-7d}\Rightarrow\dfrac{2a+13b}{2c+13d}=\dfrac{3a-7b}{3c-7d}\) (1)
Nhân tư và mẫu vế trái (1) với 3 và vế phải với 13 ta được:
\(\dfrac{2a+13b}{2c+13d}=\dfrac{14a+91b}{14c+91d}=\dfrac{39a-91b}{39c-91d}\)
=\(\dfrac{\left(14a+91b\right)+\left(39a-91b\right)}{\left(14c+91d\right)+\left(39c-91d\right)}=\dfrac{53a}{53c}=\dfrac{a}{c}\) (2)
Nhân tử và mẫu vế trái (1) với 3 và vế phải với 2 ta được:
\(\dfrac{2a+13b}{2c+13d}=\dfrac{6a+39b}{6c+39d}=\dfrac{6a-14b}{6c-14d}=\dfrac{53b}{53d}=\dfrac{b}{d}\) (3)
Từ (2) và (3) suy ra :
\(\dfrac{a}{c}=\dfrac{b}{d}\Rightarrow\dfrac{a}{b}=\dfrac{c}{d}\)
bạn nào vậy bạn mà sai mootjtis cũng là sai rồi
Cho a/b = c/d. CMR : 2a+13b/3a-7b = 2c+13d/ 3c-7d
Cho a/b = c/d. CMR : 2a+13b/3a-7b = 2c+13d/ 3c-7d
Cho a/b = c/d. CMR : 2a+13b/3a-7b = 2c+13d/ 3c-7d
Cho a/b = c/d. CMR : 2a+13b/3a-7b = 2c+13d/ 3c-7d
Cho tỉ lệ thức: \(\dfrac{2a+13b}{3a-7b}=\dfrac{2x+13d}{3c-7d}\)
Chứng minh rằng \(\dfrac{a}{b}=\dfrac{c}{d}\)
Mong được các bạn giúp!
Ta có: \(\dfrac{2a+13b}{3a-7b}=\dfrac{2c+13d}{3c-7d}\)
\(\Rightarrow\left(2a+13b\right)\left(3c-7d\right)=\left(2c+13d\right)\left(3a-7b\right)\)
\(\Rightarrow6ac+39bc-14ad-91bd=6ac+39ad-14bc-91bd\)
\(\Rightarrow6ac-6ac+39bc+14bc-14ad-39ad-91bd+91bd=0\)
\(\Rightarrow53bc-53ad=0\)
\(\Rightarrow53bc=53ad\)
\(\Rightarrow bc=ad\)
\(\Rightarrow\dfrac{a}{b}=\dfrac{c}{d}\rightarrowđpcm.\)
\(\dfrac{2a+13b}{3a-7b}=\dfrac{2c+13d}{3c-7d}\)
\(\Leftrightarrow\)(2a+13b)(3c-7d)=(2c+13d)(3a-7b)
2a(3c-7d)+13b(3c-7d)=2c(3a-7b)+13d(3a-7b)
6ac-14ad+39bc-91bd=6ac-14bc+39ad+91bd
14ad+39bc+91bd=14bc+39ad+91bd
14ad+39bc=14bc+39ad
39bc=14bc+39ad-14ad
39bc=14bc+25ad
39bc-14bc=25ad
25bc=25ad
bc=ad
Ta có: Điều đề bài cho:
\(\dfrac{a}{b}=\dfrac{c}{d}\Leftrightarrow ad=bc\left(đpcm\right)\)
Cho tỉ lệ thức (2a+13b)/(3a-7b)=(2c+13d)/(3c-7d). Cmr: a/b=c/d.
Ta có thể chứng minh :
Ta có:
2a+13/b3a−7b=2c+13d/3c−7d
=> 2a+13b/2c+13d=3a−7b/3c−7d
Áp dụng tính chất của dãy tỉ số bằng nhau ta có :
2a+13b/2c+13d=3a−7b/3c−7d=2a+13b+3a−7b/2c+13d+3c−7d=5a+6b5c+6d
Từ 5a+6b/5c+6d = > 5a/5c=6b/6d
<=> a/c=b/d
Hay: a/b=c/d (đpcm)