Làm nhanh nha,mình cần ngay
xin các bạn đấy
a,,viết các phép tính dưới dạng lũy thừa
a.9.3^5:81
b,11^20:121^3.11^4
c,(5^5)^4:5^11.5
d,20^2020+399.29^2020
b,tính giá trị biểu thức
a,2^5-6^5-3^5.4^5
c,tìm STN x biết
+…2^3<2^x<32
+...25<_5^x<_625
Đáp án:
$\begin{array}{l}
a)\\
\dfrac{{{{9.3}^5}}}{{81}} = \dfrac{{\left( {{3^2}{{.3}^5}} \right)}}{{{3^4}}}\\
= \dfrac{{{3^7}}}{{{3^4}}} = {3^3} = 27\\
b)\dfrac{{{{11}^{20}}}}{{{{121}^3}{{.11}^4}}}\\
= \dfrac{{{{11}^{20}}}}{{{{11}^{2.3}}{{.11}^4}}}\\
= \dfrac{{{{11}^{20}}}}{{{{11}^{6 + 4}}}} = {11^{10}}\\
c)\dfrac{{{{\left( {{5^5}} \right)}^4}}}{{{5^{11}}.5}} = \dfrac{{{5^{20}}}}{{{5^{12}}}} = {5^8}\\
d){20^{2020}} + {399.20^{2020}}\\
= {20^{2020}}.\left( {1 + 399} \right)\\
= {20^{2020}}.400\\
= {20^{2020}}{.20^2}\\
= {20^{2022}}\\
b)\\
{2^5} – {6^5} – {3^5}{.4^5}\\
= {2^5} – {2^5}{.3^5} – {3^5}{.2^5}{.2^5}\\
= {2^5} – {3^5}{.2^5}\left( {1 + {2^5}} \right)\\
= {2^5} – {3^5}{.2^5}.33\\
= {2^5}\left( {1 – {3^5}.33} \right)\\
c)\\
+ ){2^3} < {2^x} < 32\\
\Rightarrow {2^3} < {2^x} < {2^5}\\
\Rightarrow 3 < x < 5\\
\Rightarrow x = 4\\
+ )\\
25 \le {5^x} \le 625\\
\Rightarrow {5^2} \le {5^x} \le {5^4}\\
\Rightarrow 2 \le x \le 4\\
\Rightarrow \left[ \begin{array}{l}
x = 2\\
x = 3\\
x = 4
\end{array} \right.
\end{array}$