dau coroana!!va rogg

Răspuns:
Explicație pas cu pas:
a) 1/15 + 2/15 + 3/15 + 4/15 = (1+2+3+4)/15 = 10/15⁽⁵ = 2/3
b) 3/(4·25) + 1/(2²·5²) + 21/(2²·25) =
= 3/(4·25) + 1/(4·25) + 21/(4·25) =
= (3+1+21)/(4·25) = 25/(4·25) = 1/4