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6 tháng 12 2016
câu 2 (tỷ lệ thuận hay nghịch
\(\frac{hs6}{9}=\frac{hs7}{8}=\frac{hs8}{7}=\frac{hs9}{6}\)
\(\frac{hs6-hs8}{9-7}=\frac{60}{2}=30\)
hs6=270(em)
hs7=240(em)
hs8=210 (em)
hs9=180 (em)
16 tháng 11 2017
1> Nua chu vi khu dat hinh chu nhat la:
280:2=140(m)
Goi chieu dai va chieu rong lan luot la x,y(x,y \(\varepsilon\)N)
Theo bai ra ta co : \(\frac{x}{4}=\frac{y}{3}\)va x+y=140
Ap dung tinh chat day ti so bang nhau ta co:
\(\frac{x}{4}=\frac{y}{3}=\frac{x+y}{4+3}=\frac{140}{7}=20\)
Tu \(\frac{x}{4}=20=>x=80\)
\(\frac{y}{3}=20=>y=60\)
Vaay chieu dai va chieu rong lan luot la 80,60
Dien h khu dat hinh chu nhat la
80.60=4800(\(m^2\))
D/s:4800m^2
Day la cach lam lop 7 nha boi vi ban hocj lop 7 nen mk giai theo cach lop7.
Nho k cho mk nhe
M
16 tháng 11 2017
a) \(2\sqrt{9}+3\sqrt{16}+2\sqrt{49}\)
\(=2.3+3.4+2.7\)
\(=6+12+14\)
\(=32\)
b) \(4\sqrt{0,25}+2\sqrt{0,36}-2\sqrt{0,16}\)
\(=4.\sqrt{\frac{25}{100}}+2\sqrt{\frac{36}{100}}-2\sqrt{\frac{16}{100}}\)
\(=4.\frac{1}{2}+2.\frac{3}{5}-2.\frac{4}{25}\)
\(=2+\frac{6}{5}-\frac{8}{25}\)
\(=\frac{72}{25}\)
4 tháng 9 2015
Ta có quy luật:
1+1=12 = 1
2+2=22 = 4
3+3 = 32 = 9
..................
.......................
9 + 9 = 92 = 81
TG
3 tháng 8 2020
1) \(125^5:25^7\)
\(=\left(5^3\right)^5:\left(5^2\right)^7\)
\(=5^{15}:5^{14}\)
= 5
2) \(27^8:9^9\)
\(=\left(3^3\right)^8:\left(3^2\right)^9\)
\(=3^{24}:3^{18}\)
\(=3^6\)
3) \(36^5:6^8\)
\(=\left(6^2\right)^5:6^8\)
\(=6^{10}:6^8\)
\(=6^2\)
4) \(49^6:7^{10}\)
\(=\left(7^2\right)^6:7^{10}\)
\(=7^{12}:7^{10}=7^2\)
5) \(7^{20}:49^9\)
\(=7^{20}:\left(7^2\right)^9\)
\(=7^{20}:7^{18}=7^2\)
6) \(\frac{1}{2^{10}}:\frac{1}{8^3}\)
\(=\frac{1}{2^{10}}:\frac{1}{\left(2^3\right)^3}\)
\(=\frac{1}{2^{10}}:\frac{1}{2^9}=\frac{1}{2^{10}}.\frac{2^9}{1}=\frac{1}{2}\)
7) \(\left(-\frac{1}{2}\right)^{21}:\frac{1}{4^{10}}\)
\(=\frac{\left(-1\right)^{21}}{2^{21}}:\frac{1}{\left(2^2\right)^{10}}\)
\(=-\frac{1}{2^{21}}:\frac{1}{2^{20}}=-\frac{1}{2^{21}}.\frac{2^{20}}{1}\)
\(=-\frac{1}{2}\)
8) \(\frac{1}{16^5}:\left(-\frac{1}{2}\right)^{18}\)
\(=\frac{1}{\left(2^4\right)^5}:\frac{\left(-1\right)^{18}}{2^{18}}\)
\(=\frac{1}{2^{20}}:\frac{1}{2^{18}}\)
\(=\frac{1}{2^{20}}.\frac{2^{18}}{1}=\frac{1}{4}\)
9) \(\frac{1}{5^{30}}:\frac{1}{25^{14}}\)
\(=\frac{1}{5^{30}}:\frac{1}{\left(5^2\right)^{14}}\)
\(=\frac{1}{5^{30}}:\frac{1}{5^{28}}=\frac{1}{25}\)
TN
6 tháng 8 2016
1)
a. \(\left(3x^2-50\right)^2=5^4\)
\(\Leftrightarrow3x^4-50=625\)
\(\Leftrightarrow3x^4=675\)
\(\Leftrightarrow x^4=225\)
\(\Leftrightarrow x=\sqrt{15}\)
2)
a. \(\frac{\left(3^4-3^3\right)^4}{27^3}=\frac{3^{16}-3^{12}}{\left(3^3\right)^3}=\frac{3^{12}.3^4-3^{12}}{3^9}=\frac{3^{12}\left(3^4-1\right)}{3^9}\)
\(=\frac{3^{12}.80}{3^9}=3^3.80=27.80=2160\)
b. \(\frac{25^3}{\left(5^5-5^3\right)^2}=\frac{\left(5^2\right)^3}{5^{10}-5^6}=\frac{5^6}{5^6.5^4-5^6}=\frac{5^6}{5^6\left(5^4-1\right)}\)
\(=\frac{5^6}{5^6.624}=\frac{1}{624}\)
VM
26 tháng 2 2020
Bài 1:
a) \(0,5-\frac{5}{41}+\frac{1}{2}-\frac{36}{41}\)
\(=\frac{1}{2}-\frac{5}{41}+\frac{1}{2}-\frac{36}{41}\)
\(=\left(\frac{1}{2}+\frac{1}{2}\right)-\left(\frac{5}{41}+\frac{36}{41}\right)\)
\(=1-1\)
\(=0.\)
b) \(\left(-\frac{2}{3}+\frac{3}{7}\right):\frac{4}{5}+\left(-\frac{1}{3}+\frac{4}{7}\right):\frac{4}{5}\)
\(=-\frac{2}{3}+\frac{3}{7}:\frac{4}{5}-\frac{1}{3}+\frac{4}{7}:\frac{4}{5}\)
\(=\left[\left(-\frac{2}{3}\right)-\frac{1}{3}\right]+\left(\frac{3}{7}+\frac{4}{7}\right):\frac{4}{5}\)
\(=\left(-1\right)+1:\frac{4}{5}\)
\(=\left(-1\right)+\frac{5}{4}\)
\(=\frac{1}{4}.\)
c) \(\left(-\frac{3}{4}\right).\sqrt{\frac{16}{9}+3.\sqrt{49}}\)
\(=\left(-\frac{3}{4}\right).\sqrt{\frac{16}{9}+3.7}\)
\(=\left(-\frac{3}{4}\right).\sqrt{\frac{16}{9}+21}\)
\(=\left(-\frac{3}{4}\right).\sqrt{\frac{205}{9}}\)
\(=\left(-\frac{3}{4}\right).\frac{\sqrt{205}}{3}\)
\(=-\frac{\sqrt{205}}{4}.\)
d) \(\left(-\frac{1}{3}\right)^2.\frac{4}{11}+1\frac{5}{11}.\left(\frac{1}{3}\right)^2\)
\(=\frac{1}{9}.\frac{4}{11}+\frac{16}{11}.\frac{1}{9}\)
\(=\frac{1}{9}.\left(\frac{4}{11}+\frac{16}{11}\right)\)
\(=\frac{1}{9}.\frac{20}{11}\)
\(=\frac{20}{99}.\)
Chúc bạn học tốt!
chịu thui
+_+
\(\left(\frac{3}{7}\right)^{20}:\left(\frac{9}{49}\right)^5\)
\(=\left(\frac{3}{7}\right)^{20}:\left(\frac{3^2}{7^2}\right)^5\)
\(=\left(\frac{3}{7}\right)^{20}:\left(\frac{3}{7}\right)^{10}\)
\(=\left(\frac{3}{7}\right)^{10}\)
\(2:\left(\frac{1}{2}-\frac{2}{3}\right)^2\)
\(=2:\left(\frac{3}{6}-\frac{4}{6}\right)^2\)
\(=2:\left(\frac{-1}{6}\right)^2\)
\(=2:\frac{1}{36}=2.36\)
\(=72\)
\(\sqrt{16}+\sqrt{0,25}-\sqrt{0,36}\)
\(=4+0,5-0,6\)
\(=3,9\)