В1.
1/4а -2/3b -5/6a +3/4b=
a(1/4-5/6)-b(2/3-3/4)=
a(6/24-20/24)-b(8/12-9/12)=
(-14/24)a-(-1/12)b=
(-7/12)a+1/12b=
1/12(b-7a)
1/12(b-7a) при а=-1 2/7, в=-36
1/12*(-36-7*(-1 2/7))=
1/12*(-36-7*(-9/7))=
1/12*(-36-(-9))=
1/12*(-36+9)=
1/12*(-27)=
-27/12= -9/4= -2 1/4
В2.
41²-39² / 96²-94²=
(41-39)(41+39) / (96-94)(96+94)=
2*80 / 2*190 =
80/190= 8/19