Question

1+3+...+(2x-1)=100
Aflați x

Answer 1

Suma are x termeni [(2x-1)+1]:2=x => (1+2x-1)×x /2=100 X la a doua =100 X=10

Answer 2

In forma 1+3+5+...+(2x-1) 
x=numarul termenilor din suma ...
inseamna ca x²=100 adica x=10 ;

Sa facem o verificare:
1+3+5+7+9+11+13+15+17+19=10²=100
adica:
 2x-1=19 deci x=(19+1):2=10