1.
a) (2a-1)²=4a²-4a+1
б) (x+3y)²=x²+6y+9y²
в)
![(\frac{1}{5}x-y) (\frac{1}{5}x+y)= ((\frac{1}{5}x)^{2}-y^{2}= \frac{x^{2}}{25}-y^{2}](https://tex.z-dn.net/?f=+%28%5Cfrac%7B1%7D%7B5%7Dx-y%29++%28%5Cfrac%7B1%7D%7B5%7Dx%2By%29%3D+%28%28%5Cfrac%7B1%7D%7B5%7Dx%29%5E%7B2%7D-y%5E%7B2%7D%3D+%5Cfrac%7Bx%5E%7B2%7D%7D%7B25%7D-y%5E%7B2%7D+++)
2. а) (c-2)(c-3)-(c-1)²=c²-5c+6-c²+2c-1=-3c+5=5-3c
б) 3(a+c)²-6ac=3a²+6ac+3c²-6ac=3a²+3c²
в) (p-3)(p²+3p+9)-p³=p³-27-p³=-27
3.
![\frac{12a^{3}-3a^{2}b}{3a}= \frac{3a(4a^{2}-ab)}{3a}=a(4a-b)](https://tex.z-dn.net/?f=+%5Cfrac%7B12a%5E%7B3%7D-3a%5E%7B2%7Db%7D%7B3a%7D%3D+%5Cfrac%7B3a%284a%5E%7B2%7D-ab%29%7D%7B3a%7D%3Da%284a-b%29++)
При a=-2, b=10
a(4a-b)=(-2)(-8-10)=36
1 способ
(в обыкновенных дробях)
6 3/5 + 1 1/3 * 1,2 = 8 1/5
1) 1 1/3 * 1,2 = 4/3 * 12/10 = (2*4)/(1*5) = 8/5 = 1 3/5
2) 6 3/5 + 1 3/5 = 7 6/5 = 8 1/5
2 способ (в десятичных дробях)
6 3/5 + 1 1/3 * 1,2 = 8,2
1) 1 1/3 * 1,2 = 4/3 * 1,2 = 4 * 1,2 : 3 = 1,6
<span>2) 6 3/5 + 1,6 = 6,6 + 1,6 = 8,2</span>
7x-15=4x+3
7x-4x=3+15
3x=18
x=6
(9 - 3√x+3√x)/(3-√x)*(3 -√x)²=9(3-√x) = 9 (3 -sqrt(4/81))=9(3-2/9)=9*3 - 2=25.