Question

Determine a soma dod 40 termo fa PA (-12,- 8)

Answer 1

resolução!

r = a2 - a1

r = - 8 - ( - 12 )

r = 4

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an = a1 + ( n - 1 ) r

an = - 12 + ( 40 - 1 ) 4

an = - 12 + 39 * 4

an = - 12 + 156

an = 144

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Sn = ( a1 + an ) n / 2

Sn = ( - 12 + 144 ) 40 / 2

Sn = 132 * 40 / 2

Sn = 5280 / 2

Sn = 2640

espero ter ajudado