1.
\(\frac{4}{1.3}+\frac{4}{3.5}+\frac{4}{5.7}+...+\frac{4}{99.101}\)
\(=4\left(\frac{2}{1.3}+\frac{2}{3.5}+\frac{2}{5.7}+...+\frac{2}{99.101}\right)\)
\(=2\left(\frac{1}{1.3}+\frac{1}{3.5}+\frac{1}{5.7}+...+\frac{1}{99.101}\right)\)
\(=2\left(1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+...+\frac{1}{99}-\frac{1}{101}\right)\)
\(=2\left(1-\frac{1}{101}\right)\)
\(=\frac{200}{101}\)
2. X = - 2018
Bạn NGUYỄN ANH KIM HÂN ơi , bạn có thể giải cách làm câu 2 giúp mình chứ , mik sẽ K
a) \(\frac{x+2}{2016}+\frac{x+3}{2015}=\frac{x}{2}+1007\)
\(\frac{x+2}{2016}+1+\frac{x+3}{2015}+1=\frac{x}{2}+1009\) ( Mỗi vế cộng thêm 2 )
\(\frac{x+2018}{2016}+\frac{x+2018}{2015}-\frac{x+2018}{2}=0\)
\(\left(x+2018\right)\times\left(\frac{1}{2016}+\frac{1}{2015}-\frac{1}{2}\right)=0\)
\(x+2018=0\)
\(x=-2018\)
b) II2xI+1I.32015+30=32016+1
II2xI+1I.32015+1=32016+1
II2xI+1I.32015=32016
Vậy II2xI+1I=3
I2xI+1=3 ( vì I2xI+1>0 )
I2xI=2
2x=2 hoặc 2x=-2
x=1 hoặc -1