ajutor!!!!!!!!!!!!!!!!!!!!! ex16

a) 15 × 87 + 15 × 13 = 15 × ( 87 + 13 ) = 15 × 100 = 1 500
b) 2 456 × 2017 + 2017 × 2544 = 2017 × ( 2456 + 2544 ) =
= 2017 × 5000 = 10 085 000
c) 197 × 489 + 197 × 112 - 301 × 197 = 197 × ( 489 + 112 - 301 ) =
= 197 × ( 601 - 301 ) = 197 × 300 = 59 100
d) 78 × 13 - 8 × 78 + 26 × 78 - 78 = 2 340
= 78 × ( 13 - 8 + 26 - 1 ) =
= 78 × ( 5 + 25 ) =
= 78 × 30 =
= 2340