1+2.5+6:7=?
Những câu hỏi liên quan
tính a. 4.5^2-2^2.5+3^2.2 b. 8-7+6-5+4-3+2-1 c.3^2.13+(1^10+8).87 d.4^2.1001.4^2 e.6^2.899+7^2.1100+7^2
TÌM SỐ HỮU TỶ X BIẾT :
3^2.5^4.2.13^7- 3^2.5^4.13^6.x=0
2 VIẾT DƯỚI DẠNG LUỸ THỪA CỦA 1 SỐ NGUYÊN:
a, 123: (3^4 .6^4)
b, 5^4 . 125 .(2.5)^-5 .0,04
c, (3/7)^5 .(7/3)^-1 -(5/3)^6 : (343/625)^-2
Tính các giới hạn sau:
a) \(\lim\limits\dfrac{\sqrt[3]{n^6-7n^3-5n+8}}{n+12}\)
b) \(\lim\limits\dfrac{1}{\sqrt{3n+2}-\sqrt{2n+1}}\)
c) \(\lim\limits\dfrac{4.3^n+7^{n+1}}{2.5^n+7^n}\)
a.
\(A=\lim\frac{\sqrt[3]{n^6-7n^3-5n+8}}{n+12}=\lim \frac{\sqrt[3]{\frac{n^6-7n^3-5n+8}{n^3}}}{\frac{n+12}{n}}=\lim \frac{\sqrt[3]{n^3-7-\frac{5}{n^2}+\frac{8}{n^3}}}{1+\frac{12}{n}}\)
Ta thấy:
\(\lim\sqrt[3]{n^3-7-\frac{5}{n^2}+\frac{8}{n^3}}=\infty \)
\(\lim (1+\frac{12}{n})=1\)
Suy ra $A=\infty$
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b.
\(B=\lim\frac{1}{\sqrt{3n+2}-\sqrt{2n+1}}=\lim \frac{1}{\frac{3n+2-(2n+1)}{\sqrt{3n+2}+\sqrt{2n+1}}}=\lim \frac{\sqrt{3n+2}+\sqrt{2n+1}}{n+1}\)
\(=\lim \frac{\sqrt{\frac{3n+2}{n}}+\sqrt{\frac{2n+1}{n}}}{\frac{n+1}{\sqrt{n}}}=\lim \frac{\sqrt{3+\frac{2}{n}}+\sqrt{2+\frac{1}{n}}}{\sqrt{n}+\frac{1}{\sqrt{n}}}\)
Ta thấy:
\(\lim( \sqrt{3+\frac{2}{n}}+\sqrt{2+\frac{1}{n}})=\sqrt{3}+\sqrt{2}>0\)
\(\lim (\sqrt{n}+\frac{1}{\sqrt{n}})=\infty\)
$\Rightarrow B=\infty$
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c.
\(C=\lim \frac{4.3^n+7^{n+1}}{2.5^n+7^n}=\lim \frac{4(\frac{3}{7})^n+7}{2(\frac{5}{7})^n+1}\)
Ta thấy:
\(\lim [4(\frac{3}{7})^n+7]=4.0+7=7\) với $|\frac{3}{7}|<1$
\(\lim [2(\frac{5}{7})^n+1]=2.0+1=1\) với $|\frac{5}{7}|<1$
$\Rightarrow C=\frac{7}{1}=7$
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1.Tinh:
a)\(\frac{2^{12}.5^7+4^6.25^3}{8^5.25^3+\left(2^2.5\right)^6}\)
\(\frac{2^{12}\cdot5^7+4^6\cdot25^3}{8^5\cdot25^3+\left(2^2\cdot5\right)^6}\)
\(=\frac{2^{12}.5^7+2^{12}\cdot5^6}{2^{15}\cdot5^6+2^{12}\cdot5^6}\)
\(=\frac{2^{12}\cdot5^6\cdot\left(1\cdot5+1\right)}{2^{12}\cdot5^6\cdot\left(2^3\cdot1+1\right)}\)
\(=\frac{6}{9}\)
\(=\frac{2}{3}\)
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\(\frac{2^{12}.5^7+4^6.25^3}{8^5.25^3+\left(2^2.5\right)^6}=\frac{2^{12}.5^7+\left(2^2\right)^6.\left(5^2\right)^3}{\left(2^3\right)^5.\left(5^2\right)^3+\left(2^2\right)^6.5^6}=\frac{2^{12}.5^7+2^{12}.5^6}{2^{15}.5^6+2^{12}.5^6}\)
\(=\frac{2^{12}.5^6.\left(5+1\right)}{2^{12}.5^6.\left(2^3+1\right)}=\frac{6}{9}=\frac{2}{3}\)
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B = 1-6+2-7+3-8+4-9
C= [ 2.3.5 mũ 2 ] tất cả mũ 2phần [ 2 mũ 3 . 5].[3 mũ 2.5 mũ 3]
Tính giá trị các biểu thức sau.
a) A = 7^ 0 + 7^ 1 + 7^ 2
b) B =(7^5 + 7^9 ).(5^4 + 5^6 ).(2^3.4-2.2^4 )
c) C =3 ^2 .[(5^2 – 3) : 11] – 2^ 4 + 2.5^3
d) D = 9 ^2 − {5^ 2 − [5^ 2 − 2(4.5 − 3^ 2 )]}
1/2.5/6.1/2.11/6
Tính \(2.5+1.4-1\dfrac{3}{7}\)
\(2.5+1.4-1\dfrac{3}{7}=\dfrac{5}{2}+\dfrac{7}{5}-\dfrac{10}{7}=\dfrac{5\cdot35}{2\cdot35}+\dfrac{7\cdot14}{5\cdot14}-\dfrac{10\cdot10}{7\cdot10}=\dfrac{175}{70}+\dfrac{98}{70}-\dfrac{100}{70}=\dfrac{173}{70}\)
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\(=3,9+\dfrac{10}{7}=\dfrac{39}{10}+\dfrac{10}{7}=\dfrac{173}{70}\)
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2,5 + 1,4 - \(1\dfrac{3}{7}\)
=3,9 + \(\dfrac{10}{7}\)
=\(\dfrac{373}{70}\)
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