Question

Rezolva ecuatiile:

a) x+ (x+1)+(x+2)+.....+(x+11)=78

b) 10+20+30+...+x0 =360

c) x+11+22+33+....+77 =2x-187

Answer 1

a) X apare in ecuatie de 12 ori, deci:

x*12 + (1+2+3+4+5+6+7+8+9+10+11) = 78
x*12 + 66 = 78
x*12 = 78 - 66
x*12 = 12
x = 12/12
x = 1
 
(nu sunt sigura cum se rezolva b)

c)
x+11+22+33+44+55+66+77 = 2x - 187
x+308 = 2x-187 (adunam 187 in amandoua egalitati)
x+308+187 = 2x
x+495=2x (scadem un x din amandoua egalitati)
495=x