Question

Find S20 given

a,=3 and d=-5

Answer 1

Explanation:

Sn=n(2a+(n-1)d)

2

S20=20(2x3+(20-1)x-5)

2

S20=10(6+19x-5)

S20= 10(6-95)

S20=10x-89

S20=-890

Hope this helps you

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