2)
((4-7x³)/(2-x))-((6x²)/(2-x))=(4-7x²-6x²)/(2-x)=(4-x²)/(2-x)=(2-x)(2+x)/(2-x)=(2+x)/1=2+x
Если x=-¾, то 2+(-¾)=1¼=1,25
3)a
(b+3a)/(18a²b)+(a-4b)/(24ab²)=(4b(b+3a)+3a(a-4b)/(72а²b²)=(4b²+12ab+3a²-12ab)/(72a²b²)=(4b²+3a²)/(72a²b²)
3)г
(а-5)/(5а+25)+(3а+5)/(а²+5а)=(а-5)/(5(а+5))+(3а+5)/(а(а+5)=(а(а-5)+5(3а+5))/(5а(а+5))=(а²-5а+15а+25)/(5а(а+5))=(а²+10а+25)/(5а(а+5))=(а+5)²/(5а(а+5))=(а+5)/(5а).