Toán Lớp 6: Cho A = 1+3+3^2+3^3 +… 3^11
Chứng minh rằng :
a, a : 13
b, a : 40
Leave a reply
Register Now
Login
Lost Password
Lost your password? Please enter your email address. You will receive a link and will create a new password via email.
Toán Lớp 6: Cho A = 1+3+3^2+3^3 +… 3^11
Chứng minh rằng :
a, a : 13
b, a : 40
Comments ( 2 )
A=(1+3+3^2)+(3^3+3^4+3^5)+…….+(3^9+3^10+3^11)
A=1(1+3+3^2)+3^3(1+3+3^2)+…….+3^9+(1+3+3^2)
A=1.13+3^3. 13+……+3^9. 13
A=13.(1+3^3+….+3^9)
Vì 13vdots13
=>A vdots 13
A=1+3+3^2+3^3 +… 3^11
A=( 1 + 3 + 3^2 + 3^3 ) +…+( 3^8 + 3^9 + 3^10 + 3^11 )
A=1(1+3+3^2+3^3)+3^4(1+3+3^2+3^3)+3^8(1+3+3^2+3^3)
A=1.40+3^4. 40+3^8. 40
A=40.(1+3^4+3^8)
Vì 40vdots40
=>A vdots 40