[tex]\displaystyle\\
1)~x\cdot x=x^2\\\\
2)~\frac{1}{3}a\cdot3a^3=\frac{3a^4}{3}=a^4\\\\
3)~-3a\cdot(8d)=-24ad\\\\
4)~-4x\cdot7y=-28xy\\\\
5)~-3x\cdot2x\cdot(-x)=6x^3\\\\
6)~4a\cdot 2a^6\cdot a^{-2}=8a^{1+6-2}=8a^5\\\\
7)~ \frac{1}{3}a\cdot\frac{2}{5}b\cdot\frac{21}{4}c=\frac{1\cdot2\cdot21}{3\cdot5\cdot4}abc=\frac{42}{60}abc=\frac{7}{10}abc\\\\
8)~\sqrt{2}x^2\cdot\sqrt{2}x^3=2x^5\\\\
9)~\sqrt{3}x^2 \cdot \sqrt{2}x^5=\sqrt{6}x^7\\\\
10)~-4,\!7x\cdot10x^2=47x^3\\\\
11)~x^2b\cdot(-3x^5)=-3x^7b
[/tex]
