Tính nhanh *(a × 7 + a × 8 - a × 15) : ( 1 + 2 + 3 + ........ + 10) * ( 18 - 9 × 2) × ( 2 + 4 + 6 + 8 + 10 )
Giải thích
*(a × 7 + a × 8 - a × 15) : ( 1 + 2 + 3 + ........ + 10)
= a × (7 + 8 – 15) : ( 1 + 2 + 3 + ........ + 10)
= (a × 0) : ( 1 + 2 + 3 + ........ + 10)
= 0 : ( 1 + 2 + 3 + ........ + 10)
= 0
* ( 18 - 9 × 2) × ( 2 + 4 + 6 + 8 + 10 )
= (18 – 18) × ( 2 + 4 + 6 + 8 + 10 )
= 0×( 2 + 4 + 6 + 8 + 10 )