1). 10*0,5*a*a^2*b^3*b*b^3=5a^3b^7; 2) x*x^5*x^3*y*y^3*y^8=x^9y^12.
2. (x-3)(x-7)-2x(3x-5)
x²-7x-3x+21-6x²+10x
-5x²+21
3. 4a(a-2)-(a-4)²
4a²-8a-(a²-8a+16)
4a²-8a-a²+8a-16
3a²-16
4. 2x(x-3)-3x(x+5)
2x²-6x-3x²-15x
-x²-21x
5. (a+7)(a-1)+(a-3)²
a²-a+7a-7+(a²-6a+9)
a²-a+7a-7+a²-6a+9
2a²+2