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Tại sao làm như vậy là sai nhỉ : \(\lim\limits_{ }\frac{1+2+...+n}{n^2+1}=\lim\limits_{ }\frac{\frac{1}{n}+\frac{2}{n}+...+\frac{1}{n^2}}{1+\frac{1}{n^2}}=\frac{0}{1}=0\)
phải làm theo vầy mới đúng : \(\lim\limits_{ }\frac{1+2+...+n}{n^2+1}=\lim\limits_{ }\frac{n\left(n+1\right)}{2\left(n^2+1\right)}=\lim\limits_{ }\frac{1+\frac{1}{n}}{2+\frac{1}{n}}=\frac{1}{2}\)
Mình mới học nên ko hiểu lắm, có ai giúp vớiiiiiiiiiii
Tìm các giới hạn sau :
A=\(\lim\limits_{x\rightarrow0}\frac{\sqrt[3]{x+1}-1}{\sqrt[4]{2x+1}-1}\)
B=\(\lim\limits_{x\rightarrow7}\frac{\sqrt[3]{4x-1}\sqrt{x-2}}{\sqrt[4]{2x+2}-2}\)
C=\(\lim\limits_{x\rightarrow0}\frac{\sqrt{\left(2x+1\right)\left(3x+1\right)\left(4x+1\right)}-1}{x}\)
D=\(\lim\limits_{x\rightarrow0}\frac{\sqrt{1+4x}-\sqrt[3]{1+6x}}{x^2}\)
E=\(\lim\limits_{x\rightarrow0}\frac{\sqrt[m]{1+ax}-\sqrt[n]{1+bx}}{x}\)
Giup mình vớiii
bài 1
a. \(\lim\limits_{n\rightarrow+\infty}\left(-n^6+7n+1\right)\)
b. \(\lim\limits_{n\rightarrow+\infty}\sqrt[3]{2n^3-n+1}\)
bài 2: Tính
a. \(A=1+\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+...\)
b. B= 1+0.1+0.01+0.001+0.0001+...
tìm các giới hạn
a)lim(\(\sqrt{n+1}-\sqrt{n}\))
b)lim\(\left(\sqrt{n+5n+1}-\sqrt{n^2-n}\right)\)
c)lim\(\left(\sqrt{3n^2+2n-1}-\sqrt{3n^2-4n+8}\right)\)
d)lim\(\frac{2^n+6^n-4^{n+1}}{3^n+6^{n+1}}\)
e)lim\(\frac{3^n-4^n+5^n}{3^n+4^n-5^n}\)
f)lim\(\frac{1+3+5+.....+\left(2n+1\right)}{3n^2+4}\)
g)lim[\(\frac{1}{1.2}+\frac{1}{2.3}+....+\frac{1}{n\left(n+1\right)}\)]
h)lim\(\frac{1^2+2^2+3^2+.....+n^2}{n\left(n+1\right)\left(n+2\right)}\)
tìm giới hạn của dãy số
1.\(\lim\limits_{n->\infty}\left(\sqrt[3]{n^3+n^2+n+1}-n\right)\)
2.\(\lim\limits_{n->\infty}\left(\sqrt{n^2+n}-\sqrt{n^2-n+1}\right)\)
3.tìm a,b để \(\lim\limits_{n->\infty}\left(\sqrt{an^2+bn+2}-2n\right)=2\)
Cho n là số nguyên dương \(\ge2\). Tìm giới hạn sau :
\(L=\lim\limits_{x\rightarrow1}\frac{x^n-nx+n-1}{\left(x-1\right)^2}\)
Lim \(\frac{2^n+3^n}{3-4\cdot3^{n+1}}\)
lim \(\frac{4^{n+1}+10^n}{3^n-4\cdot10^{n+1}}\)
lim \(\frac{3^n\cdot4^n-2^n}{12^n+5\cdot3^{n+2}}\)
lim \(\frac{\left(-2\right)^n+3^n}{\left(-2\right)^{n+1}-4\cdot3^{n+1}+2}\)
lim \(\frac{3^n-11}{1+7\cdot2^{n+1}}\)
lim \(\frac{2^n-3\cdot5^n+1}{3\cdot2^n+7\cdot4^{n+1}}\)
1/ lim \(\frac{n^2-2n}{n^2-n+6}\)
2/ lim \(\frac{4n^2-6}{n^4+n^2-17}\)
3/ lim \(\frac{n^3-n^2+n}{n+7}\)
4/ lim \(\frac{\left(3-2n\right)^4}{\left(n+1\right)^2\left(n^2+1\right)}\)
tính các giới hạn sau:
a, lim\(\frac{3.2^n-8.7^n}{4.3^n+5.7^n}\)
b, lim\(\frac{2^{n+1}\left(3.2^n-3^{n-2}\right)}{3^n\left(2^{n-1}+4\right)}\)
c, lim\(\frac{\left(-3\right)^n+2.5^n}{1-5^n}\)
d, lim\(\frac{1+2+3+...+n}{n^2+n+1}\)
Tính:
Câu 1: lim ( \(\frac{1}{\sqrt{n^2+1}}\) + \(\frac{1}{\sqrt{n^2+2}}\) + ... + \(\frac{1}{\sqrt{n^2+n}}\) )
Câu 2: lim ( \(\frac{1}{1.2}\) + \(\frac{1}{2.3}\) +...+ \(\frac{1}{n\left(n+1\right)}\) )
Câu 3: lim ( \(\frac{1}{n^2}\) + \(\frac{3}{n^2}\) + \(\frac{5}{n^2}\) +...+ \(\frac{2n-1}{n^2}\) )
Câu 4: lim ( \(\sqrt{3+\frac{n^2-1}{3+n^2}}\) - \(\frac{\left(-1\right)^n}{2^n}\) )
Câu 5: lim \(\sqrt{\frac{cos2n}{3n}+9}\)