Find the sum of first 15 terms of AP2,7, 12....please ans. the questio

1.	Find the sum of first 15 terms of AP2,7, 12....please ans. the question fast
Answer» Sum of first 15 terms of A.P is 555 . Step-by-step explanation: To FIND:- Sum of first 15 terms of A.P . Solution :- Our A.P is 2, 7, 12 ..... First TERM = 2 COMMON DIFFERENCE: $\sf \leadsto a_{2} - a_{1}$ {Where , $\sf a_{2} \: is \: 7\: and \: a_{1} \: is \: 2$ } $\sf \leadsto 7 - 2$ $\sf \leadsto 5$ We know $\boxed{ \sf \bold{ S_{n} = \dfrac{n}{2} \big\{2a + (n - 1)d \big\} }}$ Where, n is number of terms, a is first term and d is common difference of A.P . Put, n, a and d in formula: $\sf \longrightarrow S_{15} = \dfrac{15}{2} \big\{2 \times 2 + (15 - 1) \times 5 \big \}$ $\sf \longrightarrow S_{15} = \dfrac{15}{2} \big\{4 + (14) \times 5 \big\}$ $\sf \longrightarrow S_{15} = \dfrac{15}{2} \big\{ 4 + 70 \big\}$ $\sf \longrightarrow S_{15} = \dfrac{60}{2} + \dfrac{1050}{2}$ $\sf \longrightarrow S_{15} = \dfrac{1110}{2}$ $\sf \longrightarrow \blue{ \boxed{ \sf \bold{S_{15} = 555}} \bigstar}$ Therefore, Sum of first 15 terms of A.P is 555.