\(\frac{3}{1.4}+\frac{3}{4.7}+...+\frac{3}{40.43}\)
\(=1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+...+\frac{1}{40}-\frac{1}{43}\)
\(=1-\frac{1}{43}\)
\(=\frac{43}{43}-\frac{1}{43}\)
\(=\frac{42}{43}\)
Chúc bạn học tốt !!!
3/1.4+3/4.7+...+3/40.43
=1/1.4+1/4.7+...+1/40.43
=1-1/4+1/4-1/7+..+1/40.43
=1-(1/4-1/4+1/7-1/7+...+1/40-1/40+1/43)
=1-1/43
=42/43
\(\frac{3}{1\cdot4}+\frac{3}{7\cdot7}+...+\frac{3}{40\cdot43}\)
\(=1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+...+\frac{1}{40}-\frac{1}{43}\)
\(=1-\frac{1}{43}\)
\(=\frac{42}{43}\)
Tâm đoàn:
\(\frac{3}{1.4}+\frac{3}{4.7}+...+\frac{3}{40.43}\)
\(=\frac{1}{1}+\left(\frac{1}{4}-\frac{1}{4}\right)+\left(\frac{1}{7}-\frac{1}{7}\right)+...-\frac{1}{43}\)
\(=1-\frac{1}{43}=\frac{43}{43}-\frac{1}{43}=\frac{42}{43}\)
Tham khảo nha!
