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a: \(3\sqrt{200}=3\cdot10\sqrt{2}=30\sqrt{2}\)
b: \(-5\sqrt{50a^2b^2}=-5\cdot5\sqrt{2a^2b^2}\)
\(=-25\cdot\left|ab\right|\cdot\sqrt{5}\)
c: \(-\sqrt{75a^2b^3}\)
\(=-\sqrt{25a^2b^2\cdot3b}=-5\left|ab\right|\cdot\sqrt{3b}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a: \(A=sin^210^0+sin^280^0+cos^220^0+sin^270^0\)
\(=sin^210^0+cos^210^0+sin^270^0+sin^270^0\)
\(=2\cdot sin^270^0+1\)
b: \(=sin^215^0+sin^275^0+sin^235^0+sin^255^0\)
\(=sin^215^0+cos^215^0+sin^235^0+cos^235^0\)
=1+1
=2
![](https://rs.olm.vn/images/avt/0.png?1311)
\(A=sin^210^0+sin^280^0+cos^220^0+sin^270^0\)
\(=sin^210^0+cos^210^0+sin^270^0+sin^270^0\)
\(=2sin^270^0+1\)
\(B=sin^215^0+sin^275^0+sin^235^0+sin^255^0\)
\(=sin^215^0+cos^215^0+sin^235^0+cos^235^0\)
=1+1
=2
![](https://rs.olm.vn/images/avt/0.png?1311)
\(A=2^1+2^2+2^3+...+2^{10}\)
\(\Rightarrow2A=2\cdot\left(2+2^2+2^3+...+2^{10}\right)\)
\(\Rightarrow2A=2^2+2^3+...+2^{11}\)
\(\Rightarrow2A-A=\left(2^2+2^3+...+2^{11}\right)-\left(2+2^2+...2^{10}\right)\)
\(\Rightarrow A=2^{11}-2\)
\(B=3^1+3^2+...+3^{100}\)
\(\Rightarrow3B=3\cdot\left(3+3^2+...+3^{100}\right)\)
\(\Rightarrow3B=3^2+3^3+...+3^{101}\)
\(\Rightarrow3B-B=\left(3^2+3^3+...+3^{101}\right)-\left(3+3^2+3^3+...+3^{100}\right)\)
\(\Rightarrow2B=3^{101}-3\)
\(\Rightarrow B=\dfrac{3^{101}-3}{2}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(A=sin^210^o+cos^220^o+sin^280^o+cos^270^o\)
\(A=\left(sin^210^o+sin^280^o\right)+\left(cos^220^o+cos^270^o\right)\)
\(A=0+0\)
\(A=0\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(A=2+2^2+...2^{2021}\)
\(\Rightarrow A+1=1+2+2^2+...2^{2021}\)
\(\Rightarrow A+1=\dfrac{2^{2021+1}-1}{2-1}\)
\(\Rightarrow A+1=2^{2022}-1\)
\(\Rightarrow A=2^{2022}-2< 2^{2022}=B\)
\(\Rightarrow A< B\)
a = 20042 + 20032 + 2002 - 20012
= ....6 + ..9 + ....0 -.... 1 = ....14 => Chữ số hàng chục là 1 (lẻ)
Khi a là SCP có chữ số tận cùng là 4 thì chữ số hàng chục phải là số chẵn
Vì vậy a không phải là SCP (đpcm)