數學 summation (詳細步驟+答案)

summation(t=12 to 17) (8t^2-5t+3)
= sum(12-17) 8t^2 - sum(12-17) 5t + sum(12-17) 3
= 8( 12^2 +13^2 +14^2 +15^2 +16^2 + 17^2) - 5(12+13+14+15+16+17) + 3(6)
= 8(1279) -5(87) +18
= 10232 - 435 + 18
= 9815

一直加到17??
即係我應該代12-17入t??
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