Răspuns:
a) (1+2+3+...+24)/25=[tex]\frac{24*25}{2}[/tex] :25= [tex]\frac{12*25}{25}[/tex]=12
b) (1+2+...+149)= [tex]\frac{149*150}{2}[/tex]= 149*75
suma fractiilor= [tex]\frac{149*75}{150}[/tex]= 149/2
d) (1+3+...+51)= 26*26
suma frc= [tex]\frac{676}{50} = 338/25[/tex]
1 + 2 + 3 + 4 + … + n = n x ( n + 1 ) : 2 formule
1 + 3 + 5 + 7 + … + ( 2n – 1 ) = n x n n = nr de termeni
n= (ultimul termen- primul): 2
