1. 2(3x+1)+3(1-2x)= 6x+2+3-6x=5
3. x•x+x-x:x=x^2 +x-1
5. x^8:x^7+x^6:x^5-x^4:x^3+x^3:x=x+x-x+x=2x
7. (x-2)(x+2)+4= x^2 -4+4= x^2
9. (x+4)(x-3)-x+12= x^2-3x+4x-12-x+12= x^2