[tex]\\ \boxed{\text{Rezolvarea clasica:}}[/tex]
[tex]f(x) = 8x-7\\ \\ \sum\limits_{x=1}^{100}f(x) = \sum\limits_{x=1}^{100}(8x-7) = \sum\limits_{x=1}^{100}8x - \sum\limits_{x=1}^{100}7 = 8\cdot \sum\limits_{x=1}^{100}x-\sum\limits_{x=1}^{100}7 = \\ \\ = 8\cdot (1+2+3+...+100)-(7+7+7+\underset{\text{de 100 ori}}{\underbrace{...}}+7) = \\ \\ = 8\cdot \dfrac{100\cdot (100+1)}{2}-7\cdot 100 = \\ \\ = 4\cdot 100\cdot 101-7\cdot 100 = \\ \\ = 100\cdot(4\cdot 101-7) = \\ \\ = 100\cdot (404-7) = \\ \\ = 100\cdot 397 = \\ \\ = 39700[/tex]
