Question

efectuati :
d) 5a + 10a + 15a +...+ 60a + 3b + 6b +...+ 36b =​

Answer 1

5 a (1+2+3+...+12)+3b (1+2+3+...+12)

(1+2+3+...+12)(5a+3b )

(12×13÷2)×15ab

78×15ab =1170ab

Answer 2

5a + 10a + 15a +...+ 60a + 3b + 6b +...+ 36b =​

= 5a·(1 + 2 + .. + 12) + 3b·(1 + 2 + .. + 12)

= (5a + 3b)·(1 + 2 + .. + 12)

= (5a + 3b)·12·13:2

= 78·(5a + 3b)