1. (а+b)²-2ab=a²+2ab+b²-2ab=a²+b²
2. (a+2b)²-9a²=a²+4ab+4b²-9a²=4ab+4b²-8a²
3. 18a+(a-9)²=18a+a²-18a+81=a²+81
4. (5x-1)²-25x²=25x²-10x+1-25x²=-10x+1
5. (x-3)²+(x+9)*x=x²-6x+9+x²+9x=2x²+3x+9
6. 2*(x-3)*(x+3)=2*(x²-9)=2x²-18
7. 2x²-(x+1)(x-1)=2x²-x²+1=x²+1
8. m*(m-4)+(3-m)(3+m)=m²-4m+9-m²=9-4m