Gọi A = 1.3+3.5+5.7+...+21.23
=> A = 1.(1+2)+3.(3+2)+5.(5+2)+...+21.(21+2)
=> A = 12+1.2+32+2.3+52+2.5+...+212+2.21
=> A = 12+32+52+...+212+(1.2+3.2+5.2+...+2.21)
Gọi B = 12+32+52+...+212
=> B = (21.22.23)/3
Gọi C = 1.2+2.3+5.2+...+2.21
=> C = 2(1+3+5+...+21)
=> C = 2{(21+1).[(21-1):2+1]}/2
=> C = 22x11=242
Vậy A = (21.22.23)/3+242
S=\(1\times3+3\times5+5\times7+...+99\times101\)
Tính \(\frac{1}{1\times3}+\frac{1}{3\times5}+\frac{1}{5\times7}+...+\frac{1}{91\times93}\)
thực hiện phép tính
A=\(\frac{3}{1\times5}+\frac{3}{5\times10}+....+\frac{3}{100\times105}\)
B=
\(\dfrac{5}{1\times3\times5}+\dfrac{5}{3\times5\times7}+...+\dfrac{5}{99\times101\times103}\)
\(\frac{9^8\times3-9^9}{9^8\times5+9^8\times7}\div\frac{11^4\times6-11^5}{11^4-11^5}\div\frac{10^5-10^5\times3}{10^511}\)
Tim n thuộc N
A = \(\frac{2}{1\times3}+\frac{2}{3\times5}+\frac{2}{5\times7}+...+\frac{2}{n\times\left(n+2\right)}<\frac{2015}{2016}\)
Tập hợp các giá trị nguyên dương của x thỏa mản :\(\left(\right)\frac{1}{1\times2}+\frac{1}{2\times3}+\frac{1}{3\times4}+\frac{1}{4\times5}+\frac{1}{5\times6}+\frac{1}{6\times7}\left(\right)\times x<\frac{13}{7}\)có số phần tử là
a.\(\frac{7^3\times5^8}{49\times25^4}\)
b.\(\frac{3^9\times25\times5^3}{15\times625\times3^8}\)
c.\(\frac{2^{50}\times3^{61}+2^{90}\times3^{16}}{2^{51}\times3^{61}+2^{91}\times3^{16}}\)
d.\((\frac{2}{5}-\frac{1}{2})^2+(\frac{1}{2}+\frac{3}{5})^2\)
thực hiện phép tính:\(A=\frac{2^{12}\times4^6\times9^2}{2^{12}\times3^6+8^4\times3^5}-\frac{5^{10}\times7^3-25^2\times49^2}{125^3\times7^3+5^9\times14^3}\)
Tính:
\(\frac{2^{12}\times3^5-4^6\times9^2}{12^6+8^4\times3^5}-\frac{5^{10}\times7^3-25^5\times49^2}{\left(125\times7\right)^3+5^9\times14^3}\)
