7Х + 2 > 23
7Х > 23- 2
7X > 21
X > 21: 7
Х> 3
D= (-1)^2-4*5*(-1)=1+20=21>0- 2 корня
x1.2= -(-1)+- <span>√21 /10 (дробью)
x1= 1+</span>5 - √21/10(дробью) = примерно 0.55826
x2=1-5 - √21 /10 (дробью) = примерно <span>-0.35826</span>
17,3*(10,5+5)+2,7*(10,5+5)
(17,3+2,7)(10,5+5)
20*11
220
![\begin{cases} \frac{x+3}{5}-\frac{x-2}{4}\leq1\\5x+8\leq38 \end{cases}](https://tex.z-dn.net/?f=%5Cbegin%7Bcases%7D+%5Cfrac%7Bx%2B3%7D%7B5%7D-%5Cfrac%7Bx-2%7D%7B4%7D%5Cleq1%5C%5C5x%2B8%5Cleq38+%5Cend%7Bcases%7D)
![\begin{cases} \frac{4(x+3)-5(x-2)-20}{20}\leq0\\5x\leq30 \end{cases}](https://tex.z-dn.net/?f=%5Cbegin%7Bcases%7D+%5Cfrac%7B4%28x%2B3%29-5%28x-2%29-20%7D%7B20%7D%5Cleq0%5C%5C5x%5Cleq30+%5Cend%7Bcases%7D)
![\begin{cases} 4x+12-5x+10-20\leq0\\x\leq6 \end{cases}](https://tex.z-dn.net/?f=%5Cbegin%7Bcases%7D+4x%2B12-5x%2B10-20%5Cleq0%5C%5Cx%5Cleq6+%5Cend%7Bcases%7D)
![\begin{cases} -x+2\leq0\\x\leq6 \end{cases}](https://tex.z-dn.net/?f=%5Cbegin%7Bcases%7D+-x%2B2%5Cleq0%5C%5Cx%5Cleq6+%5Cend%7Bcases%7D)
![\begin{cases} x-2\geq0\\x\leq6 \end{cases}](https://tex.z-dn.net/?f=%5Cbegin%7Bcases%7D+x-2%5Cgeq0%5C%5Cx%5Cleq6+%5Cend%7Bcases%7D)
![\begin{cases} x\geq2\\x\leq6 \end{cases}](https://tex.z-dn.net/?f=%5Cbegin%7Bcases%7D+x%5Cgeq2%5C%5Cx%5Cleq6+%5Cend%7Bcases%7D)
Выпишем все целые решения системы: 2,3,4,5,6
Ответ: 4