\(\dfrac{1}{1\cdot2}+\dfrac{1}{2\cdot3}+...+\dfrac{1}{9\cdot10}\)
\(=1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-...+\dfrac{1}{9}-\dfrac{1}{10}\)
\(=1-\left(\dfrac{1}{2}-\dfrac{1}{2}\right)-\left(\dfrac{1}{3}-\dfrac{1}{3}\right)-...-\left(\dfrac{1}{9}-\dfrac{1}{9}\right)-\dfrac{1}{10}\)
\(=1-\dfrac{1}{10}\)
\(=\dfrac{10}{10}-\dfrac{1}{10}\)
\(=\dfrac{9}{10}\)
tính (1/2+1/3+...+1/10)+(2/3+2/4+...+2/10)+(3/4+3/5+...+3/10)+...+(8/9+8/10)+9/10
1+1/2+1/3+1/4+....+1/8+1/9+1/10
1/1*10+1/2*9+1/3*8+......+1/8*3+1/2*9+1/10*1
B=1/1*2*3*4 + 1/2*3*4*5 + 1/3*4*5*6 + 1/8*9*10*11 + 1/9*10*11*12 = ?
1+1+1+1+2+2+2+3+3+3+3+4+4+4+4+5+5+5+5+6+6+6+6+7+7+7+7+8+8+8+8+9+9+9+9+10=
1/1+2 + 1/1+2+3 + 1/1+2+3+4 +………+1/1+2+3+4………+9+10 = ?
tính (1/2+1/3+...+1/10)+(2/3+2/4+...+2/10)+(3/4+3/5+...+3/10)+...+(8/9+8/10)+9/10
ai nhanh nhất mình tick cho nhưng phải trình bày và đúng nha
8/9÷3/7=
8/9+2/5=
7/8-1/3=
3/10×1/6=
b.hỗn số
1 2/7+6 5/6=
5 3/4-1/5 =
6 2/9÷4 7/10=
5/3+3/2-7/6=
tính
a) 1 1/6 + 1 4/9 =
b) 2 3/4 : 1 3/19 =
c) ( 4 1/5 - 2 3/10 ) x 2 1/2 =
d) 3 3/7 : 6 1/2 x 1 2/5 =
C = 5 9/10 : 3/2 - ( 2 1/3 x 4 1/2 - 2 x 2 1/3 ) : 7/4
5 9/10 ; 2 1/3 ; 4 1/2 ; 2 1/3 là hỗn sốGiúp mk nha , ai nhanh mk tick cho . Thông cảm mk ko viết được hôn số . Ahihi
