rút gọn biểu thức
\(\frac{\left(-27\right)^{10}\cdot16^{25}}{6^{30}.\left(-32\right)^{15}}\) =?
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NQ
1
12 tháng 10 2021
\(=\dfrac{3^{30}\cdot2^{100}}{2^{30}\cdot3^{30}\cdot2^{75}}=\dfrac{1}{2^5}=\dfrac{1}{32}\)
DN
1
AN
20 tháng 12 2017
Đặt giá trị biểu thức là A, ta có:
\(A=\dfrac{\left(-27\right)^{10}.16^{25}}{6^{30}.\left(-32\right)^{15}}\)
\(A=\dfrac{\left(\left(-3\right)^3\right)^{10}.\left(2^4\right)^{25}}{2^{30}.3^{30}.\left(\left(-2\right)^5\right)^{15}}\)
\(A=\dfrac{\left(-3\right)^{30}.2^{100}}{2^{30}.3^{30}.\left(-2\right)^{75}}\)
\(A=\dfrac{3^{30}.2^{100}}{2^{30}.2^{75}.3^{30}}=\dfrac{1}{2^5}=\dfrac{1}{32}\)
H9
HT.Phong (9A5)
CTVHS
5 tháng 9 2023
a) \(\left(\sqrt{14}+\sqrt{6}\right)\sqrt{5-\sqrt{21}}\)
\(=\sqrt{14}\cdot\sqrt{5-\sqrt{21}}+\sqrt{6}\cdot\sqrt{5-\sqrt{21}}\)
\(=\sqrt{14\cdot\left(5-\sqrt{21}\right)}+\sqrt{6\cdot\left(5-\sqrt{21}\right)}\)
\(=\sqrt{70-14\sqrt{21}}+\sqrt{30-6\sqrt{21}}\)
\(=\sqrt{7^2-2\cdot7\cdot\sqrt{21}+\left(\sqrt{21}\right)^2}+\sqrt{\left(\sqrt{21}\right)^2-2\cdot3\cdot\sqrt{21}+3^2}\)
\(=\sqrt{\left(7-\sqrt{21}\right)^2}+\sqrt{\left(\sqrt{21}-3\right)^2}\)
\(=\left|7-\sqrt{21}\right|+\left|\sqrt{21}-3\right|\)
\(=7-\sqrt{21}+\sqrt{21}-3\)
\(=4\)
b) \(\left(4+\sqrt{15}\right)\left(\sqrt{10}-\sqrt{6}\right)\sqrt{4-\sqrt{15}}\)
\(=\left[4\cdot\left(\sqrt{10}-\sqrt{6}\right)+\sqrt{15}\cdot\left(\sqrt{10}-\sqrt{6}\right)\right]\cdot\sqrt{4-\sqrt{15}}\)
\(=\left(4\sqrt{10}-4\sqrt{6}+\sqrt{150}-\sqrt{90}\right)\sqrt{4-\sqrt{15}}\)
\(=\left(4\sqrt{10}-4\sqrt{6}+5\sqrt{6}-3\sqrt{10}\right)\sqrt{4-\sqrt{15}}\)
\(=\left(\sqrt{10}+\sqrt{6}\right)\left(\sqrt{4-\sqrt{15}}\right)\)
\(=\sqrt{10\cdot\left(4-\sqrt{15}\right)}+\sqrt{6\cdot\left(4-\sqrt{15}\right)}\)
\(=\sqrt{40-10\sqrt{15}}+\sqrt{24-6\sqrt{15}}\)
\(=\sqrt{5^2-2\cdot5\cdot\sqrt{15}+\left(\sqrt{15}\right)^2}+\sqrt{\left(\sqrt{15}\right)^2-2\cdot3\cdot\sqrt{15}+3^2}\)
\(=\sqrt{\left(5-\sqrt{15}\right)^2}+\sqrt{\left(\sqrt{15}-3\right)^2}\)
\(=\left|5-\sqrt{15}\right|+\left|\sqrt{15}-3\right|\)
\(=5-\sqrt{15}+\sqrt{15}-3\)
\(=2\)
24 tháng 7 2016
\(=\frac{2^{12}.3^5-2^{12}.3^4}{2^{12}.3^6+2^{12}.3^5}-\frac{5^{10}.7^3-5^{10}.7^4}{5^9.7^3+5^4.2^3.7^3}\)
\(=\frac{2^{12}.3^4\left(3-1\right)}{2^{12}.3^5\left(3+1\right)}-\frac{5^{10}.7^3\left(1-7\right)}{5^4.7^3\left(5^5+2^3\right)}\)
\(=\frac{1}{6}+\frac{93750}{3133}\)
14 tháng 8 2023
\(M=\left(\dfrac{1}{3}\right)^{12}\cdot\left(\dfrac{1}{3}\right)^{-15}+\left(\dfrac{2}{5}\right)^{-4}\cdot5^{-4}\cdot32\)
\(=\left(\dfrac{1}{3}\right)^{-3}+2^{-4}\cdot32\)
\(=27+\dfrac{32}{16}=27+2=29\)
NV
Nguyễn Việt Lâm
Giáo viên
7 tháng 10 2019
\(A=\left(\sqrt{5}+3\right)\left(5-\sqrt{15}\right)=5\sqrt{5}-5\sqrt{3}+15-3\sqrt{15}\)
Bạn ghi nhầm đề thì phải, ngoặc đầu là \(\sqrt{5}+\sqrt{3}\) mới rút gọn được theo HĐT số 3
\(B=\left(4\sqrt{2}-5\sqrt{2}+3\sqrt{3}\right)\left(3\sqrt{3}+5\sqrt{2}-4\sqrt{2}\right)\)
\(=\left(3\sqrt{3}-\sqrt{2}\right)\left(3\sqrt{3}+\sqrt{2}\right)=27-2=25\)
\(C=1-\left(3\sqrt{5}-2\sqrt{5}-\sqrt{3}\right)\left(2\sqrt{5}-3\sqrt{5}-\sqrt{3}\right)\)
\(=1-\left(\sqrt{5}-\sqrt{3}\right)\left(-\sqrt{5}-\sqrt{3}\right)=1+\left(5-3\right)=3\)
\(D=\left(\sqrt{\frac{3}{2}}-\sqrt{\frac{2}{3}}\right).\sqrt{6}=\frac{\left(3-2\right)}{\sqrt{6}}.\sqrt{6}=1\)
23 tháng 9 2016
\(5.\left\{26-\left[3.\left(5+25\right)+15\right]:15\right\}+3^4\)
\(5.\left\{26-\left[3.30+15\right]:15\right\}+81\)
\(5.\left\{26-\left[90+15\right]:15\right\}+81\)
\(5.\left\{26-105:15\right\}+81\)
\(5.\left\{26-7\right\}+81\)
\(5.19+81\)
\(176\)