Question

if n-th term of Ap is 5n-3 then the sum of first 10 terms is ​

Answer 1

Answer:

given:

the sum of 1st term(5n) is 10.

so, 5n = 10

n = 10/5

n = 2.

therefore, 5 ✖ 2-3 = 7.

Answer 2

Answer:

$Given,$

$t_{n}=5_{n}-3$

$find s_{10}$

$t_{n}=5_{n}-3$

$t_{1}=5×1-3$

$a=2$

$t_{10}=5×10-3$

$t_{10}=47$

$s_{10}=\frac{n}{2}[a+t_{10}]$

$s_{10}=\frac{10}{2}[2+47]$

$s_{10}=\frac{10×49}{2}$

$s_{10}=\frac{490}{2}$

$∴\boxed{s_{10}=245}$

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