\(1+3+5+...+99+x=2+4+6+...+100\)
\(\Rightarrow\frac{\left(99+1\right)\left[\left(99-1\right):2+1\right]}{2}+x=\frac{\left(100+2\right)\left[\left(100-2\right):2+1\right]}{2}\)
\(\Rightarrow\frac{100.50}{2}+x=\frac{102.50}{2}\)
\(\Rightarrow\frac{100.50+2x}{2}=\frac{102.50}{2}\)
\(\Rightarrow2x=102.50-100.50=50\left(102-100\right)=50.2=100\)
\(\Rightarrow x=100:2=50\)
P/s: Dấu "." là dấu nhân nha bạn
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