Сразу пишу решение:
-0,4а(
![10a^{2}](https://tex.z-dn.net/?f=+10a%5E%7B2%7D+)
-
![6a^{4}](https://tex.z-dn.net/?f=++6a%5E%7B4%7D+)
+15-
![9a^{2}](https://tex.z-dn.net/?f=+9a%5E%7B2%7D+)
)=
=-
![-4a^{3}](https://tex.z-dn.net/?f=+-4a%5E%7B3%7D+)
+
![2,4a^{5}](https://tex.z-dn.net/?f=+2%2C4a%5E%7B5%7D+)
-6a+
![3,6a^{3}](https://tex.z-dn.net/?f=+3%2C6a%5E%7B3%7D+)
=
=-
![0,6a^{3}](https://tex.z-dn.net/?f=+0%2C6a%5E%7B3%7D+)
+
![2,4a^{5}](https://tex.z-dn.net/?f=+2%2C4a%5E%7B5%7D+)
-6a=привиди к одночлену стандартного вида
1) 5⁷ * 5⁻² = 5⁷⁻² = 5⁵ = 3125
2) 10⁹ : 10⁰ = 1 000 000 000 : 1= 1 000 000 000
![3)\frac{7^{-3}*7^{-4}}{7^{-8}}=7^{-3-4-(-8)}=7](https://tex.z-dn.net/?f=3%29%5Cfrac%7B7%5E%7B-3%7D%2A7%5E%7B-4%7D%7D%7B7%5E%7B-8%7D%7D%3D7%5E%7B-3-4-%28-8%29%7D%3D7)
4)16 * 2⁻⁶ = 2⁴ * 2⁻⁶ = 2⁻² = 0,25
5) 2b⁴ - b² = b²(2b² - 1)
6) 25b⁸ - 4a² = (5b⁴)² - (2a)² = (5b⁴ - 2a)(5b⁴ + 2a)