Notam cu a=numarul panselutelor plantate in prima zi
a doua zi planeaza: a+4*1 panselute
a treia zi planeaza: a+4*2 panselute
a patra zi planeaza: a+4*3 panselute
a cincea zi planeaza: a+4*4 panselute
Deci, in total:
a+(a+4*1)+(a+4*2)+(a+4*3)+(a+4*4)=105
5*a+4*(1+2+3+4)=105
5*a+40=105
5*a=65
a=13 panselute a plantat in prima zi
13+4=17 panselute a doua zi
17+4=21 panselute a treia zi
21+4=25=[tex] 5^{2} [/tex] panselute a patra zi
25+4=29 panselute a cincea zi
Se observa ca a patra zi a plantat un nr de panselute are este patrat perfect.
