tính A=1/4*9+1/9*14+1/14*19+...+1/64*69
DT
Những câu hỏi liên quan
1. a) So sánh 22013 và 31344
b) Tính A=1/4*9+1/9*14+...+1/64*69
TÍNH A=[(1/4*9)+(1/9*14)+(1/14*19)+...+(1/44*49)] x (1-3-5-7-...-49)/89
tính nhanh
a, 14:(14/3-14/9)+14:(/3+8/9)
b, 1++3+4+...+19+20
Các bạn giúp mình với
Bài 1
A=1×2×3×...×9-1×2×3×...×8-1×2×3...8×8
B=(3×4×2mũ16) mũ 2
C=70×(131313/565656+131313/727272+131313/909090)
D thực hiện phép tính : B=1/4×9+1/9×14+1/14×19+...+1/64×69
Bài 2
C)(2.x-15) mũ 5=(2.x-15) mũ 3
A=(1/4*9 + 1/9*14 + 1/14*19 + ...+ 1/44*49)*1-3-5-7-..-49/89
1/4*9+1/9*14+1/14*19+...+1/1999*2004
1/4*9+1/9*14+1/14*19+...+1/1999*2004
= 1/5 (1/4 - 1/9 + 1/9 - 1/14 + ... + 1/1999 - 1/2004)
= 1/5 (1/4 - 1/2004)
= 1/5 (501/2004 - 1/2004)
= 1/5 . 125/501
= 25/501
1/4*9+1/9*14+1/14*19+.....+1/1999*2004
\(\frac{1}{4\times9}+\frac{1}{9\times14}+\frac{1}{14\times19}+...+\frac{1}{1999\times2004}\)
\(=\frac{1}{5}\times\left(\frac{5}{4\times9}+\frac{5}{9\times14}+\frac{5}{14\times19}+...+\frac{5}{1999\times2004}\right)\)
\(=\frac{1}{5}\times\left(\frac{1}{4}-\frac{1}{9}+\frac{1}{9}-\frac{1}{14}+\frac{1}{14}-\frac{1}{19}+...+\frac{1}{1999}-\frac{1}{2004}\right)\)
\(=\frac{1}{5}\times\left(\frac{1}{4}-\frac{1}{2004}\right)\)
\(=\frac{1}{5}\times\frac{500}{2004}=\frac{25}{501}\)
tính 1/4*9+1/9*14+1/14*19+...+1/44*49 * 1-3-5-...-49/89 -19/28
M=(1/4*9+1/9*14+1/14*19+...1/44*49)*1-3-5-7-9-...-49/89=-9/28