This is going to be long but here I go
1 answer:
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Answer:
- 494
Step-by-step explanation:
Breaking down the summation into it;s component parts
= 4k - k(k + 1) ← substitute k = 19
= (4 × 19 ) - 1.5 × (19 × 20)
= 76 - (1.5 × 380)
= 76 - 570
= 494