18xy+6x-24y-8
18•1•0,45+6•1-24•0,45=-4,7
18•1•0,45=8,1
8,1+6•1=14,1
14,1-24•0,45=3,3
3,3-8=-4,7
1) -5×(-2)=10
-5×8/15=-24
2) 12×0.05-7=0.6-7=-6.4
3) 3-1.5×-1/3= 3-3/2×(-1/3)=5
4) 2×(-1)-1/3=-2-1/3=-7
![1) x^2-4x-1=a\\ x^2-4x-1-a=0\\ D=4+1+a\ \textgreater \ 0\\ a\ \textgreater \ -5](https://tex.z-dn.net/?f=1%29%C2%A0x%5E2-4x-1%3Da%5C%5C%0Ax%5E2-4x-1-a%3D0%5C%5C%0AD%3D4%2B1%2Ba%5C+%5Ctextgreater+%5C+0%5C%5C%0Aa%5C+%5Ctextgreater+%5C+-5)
![2) x^2-4x-1=-a\\ x^2-4x-1+a=0\\ D=4+1-a\ \textgreater \ 0\\ a\ \textless \ 5](https://tex.z-dn.net/?f=2%29+x%5E2-4x-1%3D-a%5C%5C%0Ax%5E2-4x-1%2Ba%3D0%5C%5C%0AD%3D4%2B1-a%5C+%5Ctextgreater+%5C+0%5C%5C%0Aa%5C+%5Ctextless+%5C+5)
Получаем промежуток -5 < a < 5
Под этот промежуток подходит ответ 4)
Сделаем замену
![8 ^{ \sqrt{-x} }=m](https://tex.z-dn.net/?f=8%20%5E%7B%20%5Csqrt%7B-x%7D%20%7D%3Dm%20)
>0 ОДЗ: x ≤ 0
Тогда
![64 ^{ \sqrt{-x} }= m^{2}](https://tex.z-dn.net/?f=64%20%5E%7B%20%5Csqrt%7B-x%7D%20%7D%3D%20m%5E%7B2%7D%20%20)
5m² - 17m + 6 = 0
D = (- 17)² - 4 * 5 * 6 = 289 - 120 = 169 = 13²
![m _{1} = \frac{17+13}{10}=3\\\\m _{2} = \frac{17-13}{10}=0,4\\\\8 ^{ \sqrt{-x} }=3\\\\2 ^{3 \sqrt{-x} }=3\\\\3 \sqrt{-x}=log _{2} 3\\\\ \sqrt{-x}= \frac{1}{3}log _{2} 3 \\\\8 ^{ \sqrt{-x} }=0,4\\\\log _{8}8 ^{ \sqrt{-x} }=log _{8} 0,4\\\\ \sqrt{-x}=log _{8}0,4\\\\x=log _{8} 0,4](https://tex.z-dn.net/?f=m%20_%7B1%7D%20%3D%20%5Cfrac%7B17%2B13%7D%7B10%7D%3D3%5C%5C%5C%5Cm%20_%7B2%7D%20%3D%20%5Cfrac%7B17-13%7D%7B10%7D%3D0%2C4%5C%5C%5C%5C8%20%5E%7B%20%5Csqrt%7B-x%7D%20%7D%3D3%5C%5C%5C%5C2%20%5E%7B3%20%5Csqrt%7B-x%7D%20%7D%3D3%5C%5C%5C%5C3%20%5Csqrt%7B-x%7D%3Dlog%20_%7B2%7D%203%5C%5C%5C%5C%20%5Csqrt%7B-x%7D%3D%20%5Cfrac%7B1%7D%7B3%7Dlog%20_%7B2%7D%203%20%5C%5C%5C%5C8%20%5E%7B%20%5Csqrt%7B-x%7D%20%7D%3D0%2C4%5C%5C%5C%5Clog%20_%7B8%7D8%20%5E%7B%20%5Csqrt%7B-x%7D%20%7D%3Dlog%20_%7B8%7D%200%2C4%5C%5C%5C%5C%20%5Csqrt%7B-x%7D%3Dlog%20_%7B8%7D0%2C4%5C%5C%5C%5Cx%3Dlog%20_%7B8%7D%200%2C4%20%20%20%20%20%20%20%20%20%20%20%20)