Question

find the sum of the of 28 terms of an ap whose nth term is 8n-5

Answer 1

an=8n-5
then a1=8(1)-5=3
        a2=8(2)-5=11
then a=3 and d=11-3=8
so sum of 28 terms
sum of n terms=n/2(2a+(n-1)d)
                        =28/2(2(3)+(28-1)8)
                        =14(6+27(8)
                        =14(6+216)
                        =14(222) = 3108

:)Hope this ans would help u....

Answer 2

Answer:

Step-by-step explanation:

an=8n-5

then a1=8(1)-5=3

        a2=8(2)-5=11

then a=3 and d=11-3=8

so sum of 28 terms

sum of n terms=n/2(2a+(n-1)d)

                        =28/2(2(3)+(28-1)8)

                        =14(6+27(8)

                        =14(6+216)

                        =14(222) = 3108

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