Explicație pas cu pas:
a. 5/21(-19,63)+5/21(-1,37)=
5/21(-1963/100)+5/21(-137/100)=
-5/21*1963/100-5/21*137/100=
-5/21(1963/100+137/100)=
-5/21(2100/100)=
-5/21*21=
-5
b. (3/5-0,4)x= -1
(3/5-4/10)x= -1
(3/5-2/5)x= -1
(1/5)x= -1
x= -1:(1/5)
x= -1*5/1
x= -5
c. -0,8:4/5+[0,(6)-8/3]*(0,4)^2=
-8/10*5/4+(6/9-8/3)*(4/10)^2=
-1+(2/3-8/3)*(2/5)^2=
-1+(-6/3)*(2^2/5^2)=
-1-2(4/25)=
-1-8/25=
-25/25-8/25=
-33/25
