4.
1) (2a-3)(a+4)-(5a-7)(a+2)=2a²+8a-3a-12-(5a²+10a-7a-14)=2a²+8a-3a-12-(5a²+3a-14)=2a²+8a-3a-12-5a²-3a+14=-3a²+2a+2
2) (3x-5)(1-x)+(6x+7)(3x+2)=3x-3x²-5+5x+18x²+12x+21x+14=41x+15x²+9=15x²+41x+9
3) (4a-1)(3a+1)-(2a-7)(3a+7)=12a²+4a-3a-1-(6a²+14a-21a-49)=12a²-4a-3a-1-(6a²-7a-49)=12a²+4a-3a-1-6a²+7a+49=6a²+8a+48
4) (1-2x)(3x-5)+(1-3x)(2x-3)=3x-5-6x²+10x+2x-3-6x²+9x=24x-8-12x²=-12x²+24x-8
5.