Răspuns:
Explicație pas cu pas:
a)-3/4+2/10=(-3x5+2x2)/20=(-15+4)/20=-11/20
11/9-5/4=(44-45)/36=-1/36
15/4-9/2=(15-18)/4=-3/4
b)x = 1,2+ 2,3 + 3,4+....+ 7,8=0=9×3+4,5=27+4,5=31,5
y=1 2/9+2 3/9+......+7 8/9=(1+2+...+7)+(1/9(2+3+...+7)=28+1/9(7x8/2-1=
=28+1/9(56-2)/2=28+54/9x2=28+3=31
x-y=31,5-31=0,5