Thay \(a=\dfrac{16}{15}\) vào biểu thức ta được

\(\dfrac{3}{4}\) x \(\dfrac{16}{15}+\dfrac{6}{5}=\dfrac{4}{5}+\dfrac{6}{5}=\dfrac{4+6}{5}=\dfrac{10}{5}=2\)

Vậy với \(a=\dfrac{16}{15}\) giá trị biểu thức là 2

A = \(\dfrac{1+5+5^2+5^3+5^4+...+5^{17}}{1+5^2+5^4+...+5^{16}}\)

Đặt tử số là B = 1 + 5 + 5² + 5³ + 5⁴ +...+ 5¹⁷

                  5B =       5 + 5² + 5³ + 5⁴ +...+ 5¹⁷ + 5¹⁸

                  5B - B = 5¹⁸ - 1

                  4B       = 5¹⁸ - 1

                    B       = (5¹⁸ - 1) : 4

Đặt mẫu số là C  = 1 + 5² + 5⁴ +...+ 5¹⁶

                    5².C =       5² + 5⁴ +...+ 5¹⁶ + 5¹⁸

                    25.C - C  =  5¹⁸ - 1

                    24C         =   5¹⁸ - 1

                        C         =    (5¹⁸ - 1): 24 

A = \(\dfrac{B}{C}\) = \(\dfrac{\dfrac{5^{18}-1}{4}}{\dfrac{5^{18}-1}{24}}\)

A = 6 

a=6 banj nha

\(\dfrac{15}{16}.\dfrac{8}{5}.\dfrac{3}{4}\)= \(\dfrac{5.3.4.2.3}{4.2.2.5.4}=\dfrac{9}{8}\)

= 120/80 x 3/4

=3/2 x3/4 

=9/8

\(\dfrac{6}{7}+\dfrac{5}{8}:5-\dfrac{3}{16}.\left(-2\right)^2=\dfrac{6}{7}+\dfrac{5}{8}:5-\dfrac{3}{16}.4=\dfrac{6}{7}+\dfrac{1}{8}-\dfrac{3}{4}=\dfrac{5}{56}\)

\(\dfrac{2}{3}+\dfrac{1}{3}.\left(-\dfrac{4}{9}+\dfrac{5}{6}\right):\dfrac{7}{12}=\dfrac{2}{3}+\dfrac{1}{3}.\dfrac{7}{18}:\dfrac{7}{12}=\dfrac{2}{3}+\dfrac{2}{9}=\dfrac{8}{9}\)

a: \(\frac{8^5\cdot\left(-5\right)^8+\left(-2\right)^5\cdot10^9}{2^{16}\cdot5^7+20^8}\)

\(=\frac{2^{15}\cdot5^8-2^5\cdot5^9\cdot2^9}{2^{16}\cdot5^7+\left(2^2\cdot5\right)^8}=\frac{2^{15}\cdot5^8-2^{14}\cdot5^9}{2^{16}\cdot5^7+2^{16}\cdot5^8}\)

\(=\frac{2^{14}\cdot5^8\left(2-5\right)}{2^{16}\cdot5^7\left(1+5\right)}=\frac{5}{2^2}\cdot\frac{-3}{6}=\frac54\cdot\frac{-1}{2}=-\frac58\)

b: \(\frac{\left(-0,25\right)^{-5}\cdot9^4\cdot\left(-2\right)^{-3}-2^{-2}\cdot6^9}{2^9\cdot3^6+6^6\cdot40}\)

\(=\frac{-2^{10}\cdot3^8\cdot\left(-\frac18\right)-\frac14\cdot2^9\cdot3^9}{2^9\cdot3^6+2^6\cdot3^6\cdot2^3\cdot5}=\frac{-2^7\cdot3^8-2^7\cdot3^9}{2^9\cdot3^6+2^9\cdot3^6\cdot5}\)

\(=\frac{-2^7\cdot3^8\left(1+3\right)}{2^9\cdot3^6\left(1+5\right)}=-\frac{1}{4\cdot3^2}\cdot\frac46=-\frac{1}{9\cdot6}=-\frac{1}{54}\)

a, a x 6 = 3 x 6 = 18

b, a + b = 4 + 2 = 6

c, b + a = 2 + 4 = 6

d, a - b = 8 - 5 = 3

e, m x n = 5 x 9 = 45

a. 18

b. 6

c. 6

d. 3

e. 45

=(4x0.25)x(2x0.5)

=1x1=1

ủa ko biết nữa ko biết nữa ko biết đáp án ở đâu

a) \(\sqrt[4]{\dfrac{1}{16}}=\dfrac{1}{2}\)

b) \(\left(\sqrt[6]{8}\right)^2=\sqrt[\dfrac{6}{2}]{8}=\sqrt[3]{8}=2\)

c) \(\sqrt[4]{3}\cdot\sqrt[4]{27}=\sqrt[4]{3\cdot27}=\sqrt[4]{81}=3\)