Tính lim \(\sqrt[n]{a}\left(a>0\right)\)
tính \(A=lim\left[n\left(\sqrt{n^2+2}-\sqrt{n^2-1}\right)\right]\)
Bậc và hệ số bằng nhau, liên hợp
\(lim\left(\dfrac{n^4+2n^2-n^4+n^2}{\sqrt{n^4+2n^2}+\sqrt{n^4-n^2}}\right)=lim\dfrac{3n^2}{n^2.1+n^2.1}==\dfrac{3}{2}\)
Tính các giới hạn sau
1,Lim\(\left(\dfrac{2n^3}{2n^2+3}+\dfrac{1-5n^2}{5n+1}\right)\)
2,a,Lim\(\left(\sqrt{n^2+n}-\sqrt{n^2+2}\right)\)
b,Lim\(\dfrac{\sqrt{n^4+3n-2}}{2n^2-n+3}\)
c,Lim\(\dfrac{\sqrt{n^2-4n}-\sqrt{4n^2+1}}{\sqrt{3n^2+1}-n}\)
\(a=\lim\left(\dfrac{2n^3\left(5n+1\right)+\left(2n^2+3\right)\left(1-5n^2\right)}{\left(2n^2+3\right)\left(5n+1\right)}\right)\)
\(=\lim\left(\dfrac{2n^3-13n^2+3}{\left(2n^2+3\right)\left(5n+1\right)}\right)=\lim\dfrac{2-\dfrac{13}{n}+\dfrac{3}{n^3}}{\left(2+\dfrac{3}{n^2}\right)\left(5+\dfrac{1}{n}\right)}=\dfrac{2}{2.5}=\dfrac{1}{5}\)
\(b=\lim\left(\dfrac{n-2}{\sqrt{n^2+n}+\sqrt{n^2+2}}\right)=\lim\dfrac{1-\dfrac{2}{n}}{\sqrt{1+\dfrac{1}{n}}+\sqrt{1+\dfrac{2}{n}}}=\dfrac{1}{2}\)
\(c=\lim\dfrac{\sqrt{1+\dfrac{3}{n^3}-\dfrac{2}{n^4}}}{2-\dfrac{2}{n}+\dfrac{3}{n^2}}=\dfrac{1}{2}\)
\(d=\lim\dfrac{\sqrt{1-\dfrac{4}{n}}-\sqrt{4+\dfrac{1}{n^2}}}{\sqrt{3+\dfrac{1}{n^2}}-1}=\dfrac{1-2}{\sqrt{3}-1}=-\dfrac{1+\sqrt{3}}{2}\)
a) \(lim\left(2n-\sqrt{9n^2+n}+\sqrt{n^2+2n}\right)\)
b)\(lim\sqrt{3^{n+1}+1}\)
c)\(lim\left(n+1+2^n\right)\)
Tính các giới hạn
a) \(\lim\limits_{x\rightarrow+\infty}\sqrt[3]{x^3+3x^2}-\sqrt{x^2-2x}\)
b) \(\lim\limits_{x\rightarrow+\infty}\sqrt[n]{\left(x+a_1\right)\left(x+a_2\right)...\left(x+a_n\right)}-x\)
\(\lim\limits_{x\rightarrow+\infty}\left(\sqrt[n]{\left(x+a_1\right)\left(x+a_2\right)...\left(x+a_n\right)}-x\right)\\ =\lim\limits_{x\rightarrow+\infty}\left(\dfrac{\left(x+a_1\right)\left(x+a_2\right)...\left(x+a_n\right)-x^n}{\sqrt[n]{\left(\left(x+a_1\right)\left(x+a_2\right)...\left(x+a_n\right)\right)^{n-1}}+...+x^{n-1}}\right)\)
= hệ số xn-1 trên tử/hệ số xn-1 dưới mẫu = \(\dfrac{a_1+a_2+...+a_n}{n}\)
tính các giới hạn sau:
a) lim (3n2+n2-1)
b)lim \(\dfrac{n^3+3n+1}{2n-n^3}\)
c) lim \(\dfrac{-2n^3+3n+1}{n-n^2}\)
d) lim \(\left(n+\sqrt{n^2-2n}\right)\)
e) lim \(\left(2n-3.2^n+1\right)\)
f) lim \(\left(\sqrt{4n^2-n}-2n\right)\)
g) lim \(\left(\sqrt{n^2+3n-1}-\sqrt[3]{n^3-n}\right)\)
a/ Bạn coi lại đề bài, 3n^2 +n^2 thì bằng 4n^2 luôn chứ ko ai cho đề bài như vậy cả
b/ \(\lim\limits\dfrac{\dfrac{n^3}{n^3}+\dfrac{3n}{n^3}+\dfrac{1}{n^3}}{-\dfrac{n^3}{n^3}+\dfrac{2n}{n^3}}=-1\)
c/ \(=\lim\limits\dfrac{-\dfrac{2n^3}{n^2}+\dfrac{3n}{n^2}+\dfrac{1}{n^2}}{-\dfrac{n^2}{n^2}+\dfrac{n}{n^2}}=\lim\limits\dfrac{-2n}{-1}=+\infty\)
d/ \(=\lim\limits\left[n\left(1+1\right)\right]=+\infty\)
e/ \(\lim\limits\left[2^n\left(\dfrac{2n}{2^n}-3+\dfrac{1}{2^n}\right)\right]=\lim\limits\left(-3.2^n\right)=-\infty\)
f/ \(=\lim\limits\dfrac{4n^2-n-4n^2}{\sqrt{4n^2-n}+2n}=\lim\limits\dfrac{-\dfrac{n}{n}}{\sqrt{\dfrac{4n^2}{n^2}-\dfrac{n}{n^2}}+\dfrac{2n}{n}}=-\dfrac{1}{2+2}=-\dfrac{1}{4}\)
g/ \(=\lim\limits\dfrac{n^2+3n-1-n^2}{\sqrt{n^2+3n-1}+n}+\lim\limits\dfrac{n^3-n^3+n}{\sqrt[3]{\left(n^3-n\right)^2}+n.\sqrt[3]{n^3-n}+n^2}\)
\(=\lim\limits\dfrac{\dfrac{3n}{n}-\dfrac{1}{n}}{\sqrt{\dfrac{n^2}{n^2}+\dfrac{3n}{n^2}-\dfrac{1}{n^2}}+\dfrac{n}{n}}+\lim\limits\dfrac{\dfrac{n}{n^2}}{\dfrac{\sqrt[3]{\left(n^3-n\right)^2}}{n^2}+\dfrac{n\sqrt[3]{n^3-n}}{n^2}+\dfrac{n^2}{n^2}}\)
\(=\dfrac{3}{2}+0=\dfrac{3}{2}\)
a) lim \(\left(-3n^3+n^2-1\right)\)
minh le oi ban dao mau so cua ban len cho tu uong roi thay vi tri cua mau thanh n3 +2n
Biết \(\lim\limits_{x\rightarrow+\infty}\left(\sqrt{4x^2-3x+1}-\left(ã+b\right)\right)=0\)
Tính a-4b
\(\lim\limits_{x\rightarrow+\infty}\left(\sqrt{4\text{x}^2-3\text{x}+1}-\left(ax+b\right)\right)\\ =\lim\limits_{x\rightarrow+\infty}\left(\dfrac{4\text{x}^2-3\text{x}+1-\left(ax+b\right)^2}{\sqrt{4\text{x}^2-3\text{x}+1}+\left(ax+b\right)}\right)\\= \lim\limits_{x\rightarrow+\infty}\left(\dfrac{\left(4-a\right)\text{x}^2-\left(3+2\text{a}b\right)\text{x}+1+b^2}{\sqrt{4\text{x}^2-3\text{x}+1}+\left(ax+b\right)}\right)=0\\ \Rightarrow\left\{{}\begin{matrix}4-a=0\\3+2\text{a}b=0\\2+a\ne0\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}a=4\\b=-\dfrac{3}{8}\\\end{matrix}\right.\)
Tính các giới hạn sau :
a) \(\lim\limits\left(n^2+2n-5\right)\)
b) \(\lim\limits\left(-n^3-3n^2-2\right)\)
c) \(\lim\limits\left[4^n+\left(-2\right)^n\right]\)
d) \(\lim\limits n\left(\sqrt{n^2-1}-\sqrt{n^2+2}\right)\)
Tìm các giới hạn sau:
\(a,lim\dfrac{\sqrt[3]{8n^3+2n}}{-n+3}\)
\(b,lim\dfrac{\left(2n\sqrt{n}+1\right)\left(\sqrt{n}+3\right)}{\left(n-1\right)\left(3-2n\right)}\)
\(a,lim\dfrac{^3\sqrt{8n^3+2n}}{-n+3}\)
\(=lim\dfrac{^3\sqrt{8+\dfrac{2}{n^2}}}{-1+\dfrac{3}{n}}=\dfrac{^3\sqrt{8}}{-1}=\dfrac{2}{-1}=-2\)
\(\lim\dfrac{\left(2n\sqrt{n}+1\right)\left(\sqrt{n}+3\right)}{\left(n-1\right)\left(3-2n\right)}=\lim\dfrac{\left(2+\dfrac{1}{n\sqrt{n}}\right)\left(1+\dfrac{3}{\sqrt{n}}\right)}{\left(1-\dfrac{1}{n}\right)\left(\dfrac{3}{n}-2\right)}=\dfrac{2.1}{1.\left(-2\right)}=-1\)
Tính các giới hạn sau :
a) \(\lim\limits\left(n^3+2n^2-n+1\right)\)
b) \(\lim\limits\left(-n^2+5n-2\right)\)
c) \(\lim\limits\left(\sqrt{n^2-n}-n\right)\)
d) \(\lim\limits\left(\sqrt{n^2-n}+n\right)\)
a) lim (n3 + 2n2 – n + 1) = lim n3 (1 + ) = +∞
b) lim (-n2 + 5n – 2) = lim n2 ( -1 + ) = -∞
c) lim ( - n) = lim
= lim = lim = lim = .
d) lim ( + n) = lim ( + n) = lim n ( + 1) = +∞.