Toán Lớp 6: Bài 15 Chứng tỏ rằng
1/101+1/102+…..+1/299+1/300> 2/3
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: Bài 15 Chứng tỏ rằng
1/101+1/102+…..+1/299+1/300> 2/3
Comments ( 2 )
$\begin{cases} \dfrac{1}{101} > \dfrac{1}{300} \\ \dfrac{1}{102} > \dfrac{1}{300} \\ \dfrac{1}{103} > \dfrac{1}{300} \\ … \\ \dfrac{1}{299} > \dfrac{1}{300}\end{cases}$
=> 1/101 + 1/102 + 1/103 + … + 1/299 + 1/300 > \underbrace{1/300 + 1/300 + 1/300 + … + 1/300 + 1/300}_{200 \text{lần}}
=> 1/101 + 1/102 + 1/103 + … + 1/299 + 1/300 > 200/300
=> 1/101 + 1/102 + 1/103 + … + 1/299 + 1/300 > 2/3 (đpcm)
1/101 + 1/102 + … + 1/299 + 1/300 > 2/3
1/101> 1/300; 1/102> 1/300+ …+1/300= 1/300
1/101 + 1/102 + … + 1/299 + 1/300 > 1/300+ 1/300+ …+1/300= 200/300= 2/3
1/101 + 1/102 + … + 1/299 + 1/300 > 2/3