Question

Tìm X :

a, 3/1.4+3/4.7+...+1/x.(x+3)=100/101

 

Answer 1

Đoạn cuối đáng là \(\frac{3}{x.\left(x+3\right)}\) nhưng bạn ghi lộn nha!

\(\Rightarrow1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+.....+\frac{1}{x}-\frac{1}{x+3}=\frac{100}{101}\)

\(\Rightarrow1-\frac{1}{x+3}=\frac{100}{101}\)

\(\Rightarrow\frac{x+2}{x+3}=\frac{100}{101}\Rightarrow x=100-2\)

\(\Rightarrow x=98\)

Answer 2

\(\frac{3}{1.4}+\frac{3}{4.7}+......+\frac{1}{x.\left(x+3\right)}=\frac{100}{101}\)

\(\Rightarrow1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+........+\frac{1}{x}-\frac{1}{x+3}=\frac{100}{101}\)

\(\Rightarrow1-\frac{1}{x+3}=\frac{100}{101}\)

\(\Rightarrow\frac{1}{x+3}=1-\frac{100}{101}\)

\(\Rightarrow\frac{1}{x+3}=\frac{1}{101}\)

\(\Rightarrow x+3=101\)

\(\Rightarrow x=98\)

Answer 3

 thanks 2 bạn nha