Seven o'clock (n) : 7 giờ 

\(3^x+3^{x+1}+3^{x+2}=2080-3^{x+3}\\ 3^x+3^{x+1}+3^{x+2}+3^{x+3}=2080\\ 3^x+3^x.3+3^x.3^2+3^x.3^3=2080\\ 3^x\left(1+3+9+27\right)=2080\\ 3^x.40=2080\\ 3^x=2080:40\\ 3^x=52\)

Không có cơ số 3 nào có số mũ mà bằng 52

Vậy \(x\in\left\{\varnothing\right\}\)

a, (x-25)³=8

(x-25)³=2³

x-25=2

x=2+25

x=27

Vậy x=27

b, (x+1)²=16

(x+1)²=4² hoặc (-4)²

(x+1)²=4²          (x+1)²=(-4)^2

x+1=4                 x+1=-4

x=4-1                  x=-4-1

x=3                     x=-5

Vậy xϵ{3;-5}

18(x-6)=0

x-6=0:18

x-6=0

x=0+6

x=6

Vậy x=6

Em đăng kí nhận GP ạ.

Em đăng kí nhận coin ạ.

Em đăng kí nhận quà khảo sát ạ. 

\(5^3+5^2-50\\ =125+25-50\\ =150-50\\ =100\)

\(A=\left(\dfrac{1}{2^2}-1\right)\left(\dfrac{1}{3^2}-1\right)\left(\dfrac{1}{4^2}-1\right)...\left(\dfrac{1}{100^2}-1\right)\\ A=\left(\dfrac{1}{4}-1\right)\left(\dfrac{1}{9}-1\right)\left(\dfrac{1}{16}-1\right)...\left(\dfrac{1}{10000}-1\right)\\ A=-\dfrac{3}{4}.\left(-\dfrac{8}{9}\right).\left(-\dfrac{15}{16}\right)...\left(-\dfrac{9999}{10000}\right)\\ A=\dfrac{3}{4}.\dfrac{8}{9}.\dfrac{15}{16}...\dfrac{9999}{10000}\\ A=\dfrac{1.3}{2.2}.\dfrac{2.4}{3.3}.\dfrac{3.5}{4.4}...\dfrac{99.101}{100.100}\\ A=\dfrac{1.2.3...99}{2.3.4...100}.\dfrac{3.4.5...101}{2.3.4...100}\\ A=\dfrac{1}{100}.\dfrac{101}{2}=\dfrac{101}{200}\)

Vậy \(A=\dfrac{101}{200}\)