1) 6b² - (2b+5)(3b-7)=6b² - (6b²+15b-14b-35)=6b²-6b²-b+35=35-b;
2) 16x²-(4x+0,5)(4x-0,5)=16x²-(16x²-0,25)=16x²-16x²+0,25=0,25
3) 2y(y-1.5x)-5(x+4y)(y-x)= (2y²-3xy)-5(xy+4y²-x²+4xy)=2x²-3xy-5xy-20y²+5x²-20xy=7x²-28xy-20y²
4) 3(a-2b)(2b+a)-0.5b(a-24b)=6ab-12b²+3a²-6ab-0,5ab+12b=3a²-0,5ab-12b²+12b