(√63-√28)*√7=(√9*7-√4*7)√7=(3√7-2√7)√7=√7*√7=7
<h2>Задание 1</h2>
Стандартный вид - это вид типа ![\bf n\cdot10^{a}](https://tex.z-dn.net/?f=%5Cbf+n%5Ccdot10%5E%7Ba%7D)
![\bf 1218=1.218\cdot 10^{3}](https://tex.z-dn.net/?f=%5Cbf+1218%3D1.218%5Ccdot+10%5E%7B3%7D)
<h2>Задание 2</h2>
![\bf\displaystyle\frac{a^{8}\cdot a^{5}}{a^{4}}=\frac{a^{8+5}}{a^{4}}=\frac{a^{13}}{a^{4}}=a^{13-4}=a^{9}](https://tex.z-dn.net/?f=%5Cbf%5Cdisplaystyle%5Cfrac%7Ba%5E%7B8%7D%5Ccdot+a%5E%7B5%7D%7D%7Ba%5E%7B4%7D%7D%3D%5Cfrac%7Ba%5E%7B8%2B5%7D%7D%7Ba%5E%7B4%7D%7D%3D%5Cfrac%7Ba%5E%7B13%7D%7D%7Ba%5E%7B4%7D%7D%3Da%5E%7B13-4%7D%3Da%5E%7B9%7D)
![\bf\displaystyle (a^{3})^{4}\cdot a^{5}=a^{3\cdot 4}\cdot a^{5}=a^{12}\cdot a^{5}=a^{12+5}=a^{17}](https://tex.z-dn.net/?f=%5Cbf%5Cdisplaystyle+%28a%5E%7B3%7D%29%5E%7B4%7D%5Ccdot+a%5E%7B5%7D%3Da%5E%7B3%5Ccdot+4%7D%5Ccdot+a%5E%7B5%7D%3Da%5E%7B12%7D%5Ccdot+a%5E%7B5%7D%3Da%5E%7B12%2B5%7D%3Da%5E%7B17%7D)
1/x+1/y+1/z+1/t - ?
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___+1/y+1/z+1/t =1/4
1/x+___+1/z+1/t =1/3
1/x+1/y+______ = 1/6
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сложим все три уравнения и разделим на два
1/x+1/y+1/z+1/t =(1/4+1/3+1/6)/2 =(3+4+2)/24 = 1/ (24/9)=1/ (8/3)
ответ за 8/3 часов = 2 часа 40 минут