Question

Find an Ap whose sum to n terms is 5n-2n²​

Answer 1

Answer:

$\huge{\pink{\boxed{\green{\sf{A.P=3,-1,-5,-9,-13}}}}}$

Step-by-step explanation:

$\huge{\pink{\boxed{\green{\underline{\red{\sf{SOLUTION-}}}}}}}$

${ \pink{ \boxed{ \green{ sn = 5n - 2 {n}^{2} }}}} \\ \\ take \: n = 1.2.3.4 \: \\ \to s1 = 5 \times 1 - 2 \times {1}^{2} \\ \to s1 = 5 - 2 \\ \to s1 = 3 = a1 \\ \\ \to s2 = 5 \times 2 - 2 \times {2}^{2} \\ \to s2 = 10 - 8 \\ \to \: s2 = 2 \\ \\ \to a2 = s2 - s1 \\ \to \: a2 = 2 - 3 \\ \to a2 = - 1 \\ \\ \to common \: difference = a2 - a1 \\ \to - 1 - 3 \\ \to - 4$

☆ We get first term, common difference so we can find A.P:

${ \pink{ \boxed {\green{a.p = 3, - 1 , - 5, - 9 ,- 13}}}}$

$\huge{\pink{\boxed{\green{\sf{A.P=3,-1,-5,-9,-13}}}}}$

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