Question

if sum
of n terms of AP is 3n square /2 +5n/2 then find it's 28th term

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Answer 1

Answer:

28th term is 235

Step-by-step explanation:

Let Sn = 3n²+5n/2

S28 = 3(28)²+5(28)/2 = 1246

S27 = 3(27)²+5(27)/2 = 1011

S28-S27 = 28th term

therefore 28th term is 235

Answer 2

Answer:

85

Step-by-step explanation:

given Sn=(3n^2+5n)/2

we know that Sn-S(n-1)=An

so S28-S27=A27

S28-S27=(3*28*28+5*28)/2-(3*27*27+5*27)/2

=(2352+140)/2-(2187+135)/2

=1246-1161=85

so A28=85