cho a hỏi là x hay nhân

\(\frac{3^4.5-3^6}{3^4.13+3^4}=\frac{3^4.5-3^4.3^2}{3^4.13+3^4.1}\)

                    \(=\frac{3^4.\left(5-3^2\right)}{3^4.\left(13+1\right)}\)

                    \(=\frac{5-9}{13+1}\)

                    \(=\frac{-4}{14}=\frac{-2}{7}\)

Đặt \(A=1+3^2+3^4+...+3^{100}\)

\(9A=3^2+3^4+3^6+...+3^{102}\)

\(9A-A=\left(3^2+3^4+3^6+...+3^{102}\right)-\left(1+3^2+3^4+...+3^{100}\right)\)

\(8A=3^{102}-1\)

\(A=\frac{3^{102}-1}{8}\)

Vậy \(A=\frac{3^{102}-1}{8}\)

Chúc bạn học tốt ~ 

Đặt A = 1 + 3^2 + 3^4 + 3^6 + ....+ 3^100

3^2A = 3^2 + 3^4 + 3^6 + ..+3^102

8A=3^2A - A = 3¹⁰² - 1

A = 3¹⁰² - 1/8

=. A = 3¹⁰² - 1 /8

1-2+3-4+5-6...+2015-2016

= (1 - 2) + (3 - 4) + (5 - 6) + ... + (2015 - 2016)

= -1 + (-1) + (-1) + ... + (-1) có 1008 số -1

= -1.1008

= -1008

 1 - 2 + 3 - 4 + 5 - 6 + ... + 2015 - 2016 

= ( 1- 2) + (3 - 4) + ( 5 - 6 ) + .... + (2015 - 2016 )

= ( -1 ) + (-1) + ( -1 ) + ..... + (-1)     [ Có 1008 số ( -1 ) ]

= ( -1 ) . 1008 

= -1008

A = 1+(2-3-4+5)+(6-7-8+9)+......+(97-98-99+100) - 100

   = 1+0+0+.....+0-100

   = -99

Tk mk nha

\(\cdot DuyNam\)

\(A=-\dfrac{7}{21}+\left(1+\dfrac{1}{3}\right)\)

\(A=-\dfrac{7}{21}+\dfrac{4}{3}\)

\(A=1\)

\(B=\dfrac{2}{15}+\left(\dfrac{5}{9}+-\dfrac{6}{9}\right)\)

\(B=\dfrac{2}{15}+-\dfrac{1}{9}\)

\(B=\dfrac{1}{45}\)

\(C=\left(-\dfrac{1}{5}+\dfrac{3}{12}\right)+-\dfrac{3}{4}\)

\(C=\dfrac{1}{20}+-\dfrac{3}{4}\)

\(C=-\dfrac{7}{10}\)

C = 1 - 2 - 3 + 4 + 5 - 6 - 7 + 8 +...+ 993 - 994 - 995 + 996 + 997

C = (1 - 2 - 3 + 4) + (5 - 6 - 7 + 8)+ ... +(993 - 994 - 995 + 996) + 997

C = 0 + 0 +... + 0 + 997 = 997