(a+b+c+d)(a-b-c+d)=(a-b+c-d)(a+b-c-d)
=>\(\left(a+d\right)^2-\left(b+c\right)^2=\left(a-d\right)^2-\left(b-c\right)^2\)
=>\(\left(a+d\right)^2-\left(a-d\right)^2=\left(b+c\right)^2-\left(b-c\right)^2\)
=>(a+d-a+d)(a+d+a-d)=(b+c-b+c)(b+c+b-c)
=>\(2d\cdot2a=2c\cdot2b\)
=>ad=bc
=>\(\frac{a}{c}=\frac{b}{d}\)
CMR: nếu (a+b+c+d).(a-b-c+d)=(a-b+c-d).(a+b-c-d) thì a/c= b/d
Giúp mik với ạ
Cmr nếu có
(a+b+c+d).(a-b-c+d)=(a-b+c-d).(a+b-c-d) thì a/b=c/d
cho a/b, c/d với a,b,c,d thuộc Z, b,d >0
CMR:
a , nếu a/b <c/d thì ad<bc
b,nếu a/b < c/d thì a/b < a+c/b+d<c/d
CMR : Nếu (a + b + c + d )(a - b - c + d ) = ( a - b + c - d ) ( a + b - c - d ) thì a / c = b / d
CMR nếu: (x + y - c - d)(a - b - c - d) = (a+b - c - d)(a-b+c+d) thì \(\frac{a+b}{a-b}=\frac{c-d}{c+d}\)
cmr a,nếu a/b=c/d thì a+b/b+c=c+d/d
cmr nếu a/b < c/d (b,d >0) thì a/b < a+c/b+d < c/d
a) Cho \(\dfrac{a}{b}\)=\(\dfrac{c}{d}\) CMR: \(\dfrac{5a+3b}{5a-3b}\)=\(\dfrac{5c+3d}{5c-3d}\)
b) CMR: Nếu \(\dfrac{a}{b}\)=\(\dfrac{c}{d}\) thì : \(\dfrac{a}{b}\)=\(\dfrac{3a+2c}{3b+2d}\)
c) CMR: Nếu \(\dfrac{a}{b}\)=\(\dfrac{c}{d}\) thì \(\dfrac{7a^2+3ab}{11a^2-8b^2}\) = \(\dfrac{7c^2+3cd}{11c^{2^{ }}-8d^2}\)
CMR nếu a/b<c/d thì a/b<a+c/b+d<c/d
