Cho A=196/197+197/198 và B= 196+197/197+198. So sánh A và B.
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\(\dfrac{196}{197+198}< \dfrac{196}{197};\dfrac{197}{197+198}< \dfrac{197}{198}\)
=>B<A
\(A=\frac{196}{197}+\frac{197}{198}=\left(1-\frac{1}{197}\right)+\left(1-\frac{1}{198}\right)=1-\frac{1}{197}+1-\frac{1}{198}=1-\frac{1}{197}+\frac{197}{197}-\frac{1}{198}\)\(=1-\frac{198}{197}-\frac{1}{198}=\frac{197}{197}-\frac{198}{197}-\frac{1}{198}=\frac{-1}{197}-\frac{1}{198}
B=\(\frac{196+197}{197+198}\)= \(\frac{196}{197+198}\)+ \(\frac{197}{197+198}\)
ta có \(\frac{196}{197+198}\)< \(\frac{196}{197}\)
\(\frac{197}{197+198}\)< \(\frac{197}{198}\)
=> \(\frac{196}{197+198}\)+ \(\frac{197}{197+198}\)< \(\frac{196}{197}\)+ \(\frac{197}{198}\)
=> B < A
Vi 196/197 =196/197
=>ta so sanh 197/198 va 198
198=39204/198
197/198 < 39204/198 (vi 197 < 39204 )
=>A < B
Vay A < B
Do \(\frac{196}{197}>\frac{196}{197+198}\)
\(\frac{197}{198}>\frac{197}{197+198}\)
\(\Rightarrow\frac{196}{197}+\frac{197}{198}>\frac{196}{197+198}+\frac{197}{197+198}=\frac{196+197}{197+198}\)
Vậy A > B
\(A=\frac{196}{197}+\frac{197}{198}\)và \(B=\frac{196+197}{197+198}\)
\(B=\frac{196}{197+198}+\frac{197}{197+198}\)
\(\frac{196}{197}>\frac{196}{197+198}\)và \(\frac{197}{198}>\frac{197}{197+198}\)
\(\Rightarrow A>B\)
\(Do:\frac{196}{197}>\frac{196}{197+198}\)
\(\frac{197}{198}>\frac{197}{197+198}\)
\(\Rightarrow\frac{196}{197}+\frac{197}{198}>\frac{196}{197+198}+\frac{197}{197+198}=\frac{196+197}{197+198}\)
Vậy : \(A>B\)
\(B=\frac{196+197}{197+198}=\frac{196}{197+198}+\frac{197}{197+198}\)
\(\frac{196}{197}>\frac{196}{197+198};\frac{197}{198}>\frac{197}{197+198}\)
=>A>B