Question

va implorrr,dau coroanaa!​

Answer 1

Răspuns:

x = 125

Explicație pas cu pas:

$5 + 10 + 15 + 20 + ... + 1075 + 1080 = \\ = 5 \cdot (1 + 2 + 3 + 4 + ... + 215 + 216) \\ = 5 \cdot \frac{216 \cdot 217}{2} = 117180$

$4 + 8 + 12 + 16 + ... + 956 + 960 = \\ = 4\cdot(1 + 2 + 3 + 4 + ... + 239 + 240) \\ = 4\cdot \frac{240\cdot241}{2} = 115680$

$117180 = 115680 + 12x$

$12x = 117180 - 115680$

$12x = 1500 \implies \bf x = 125$