\(=\dfrac{1}{2}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{6}+...+\dfrac{1}{50}-\dfrac{1}{52}=\dfrac{1}{2}-\dfrac{1}{52}=\dfrac{25}{52}\)
Rút gọn A =2.4+4.8+8.12+12.16+16.20/1.2+2.4+4.6+6.8+8.10
tính 2.4+3.5+4.6+5.7+6.8+7.9+8.10+...+97.99+98.100
B=\(\dfrac{1}{2.4}\)+\(\dfrac{1}{4.6}\)+\(\dfrac{1}{6.8}\)+\(\dfrac{1}{8.10}\)
2/2.4+2/4.6+2/6.8+...+2/98.100
Rút gọn A=2.4+4.8+8.12+12.16+16.20/1.2+4.6+6.8+8.10 Vậy A=
S=1/2.4+1/4.6+1/6.8+1/8.10 tính S
H=2/2.4+2/4.6+2/6.8+...+2/68.70 = ?
1 phần 2.4 cộng 1 phần 4.6 cộng 1 phần 6.8 cộng 1 phần 8.10
2/2.4+2/4.6+2/6.8+.....+2/n.(n+2)=49/100
