[tex]\it (x+2)+(x+4)+(x+6)+\ ...\ +(x+100)=2700[/tex]
Parantezele conțin numerele pare cosecutive de la 2 la 100.
Prin urmare avem 50 de paranteze, iar acum vom scrie:
[tex]\it \underbrace{x+x+x+\ ...\ +x}_{50\ termeni}+(2+4+6+\ ...\ +100)=2700 \Rightarrow \\ \\ \\ \Rightarrow 50x+2(1+2+3+\ ...\ +50)=2700 \Rightarrow 50x+2\cdot\dfrac{50\cdot51}{2}=2700 \Rightarrow \\ \\ \\ \Rightarrow 50x+2550=2700|_{-2550} \Rightarrow 50x=150|_{:50} \Rightarrow x=3[/tex]
