Question

What is the 20th term of a arithmetic sequence when first term is 7 and common difference is 3

Answer 1

$\huge\underline{\underline{\bf\bigstar ANSWER \bigstar }}$

Given ,

First term , a  = 7

Common Difference. d = 3

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     $\bf\boxed{\bf x_n=a+(n-1)d}$

$\longrightarrow\sf x_{20} = 7+(20-1)3\\\\\longrightarrow x_{20} = 7 + 19\times 3\\\\\longrightarrow x_{20} = 7 + 57 \\\\\longrightarrow\bf x_{20} = 64$

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20th term = 64

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Answer 2

$\tt \huge{answer : }$

$\sf \huge \star \: n = 20 \\ \\ \sf \huge \star \:a = 7 \\ \\ \sf \huge \star \:d = 3 \\ \\ \tt \huge \underline{formula : } \\ \\ \bf {\huge {\bigstar {\boxed{ \red{T_n = a + (n - 1)d}}}}}$

$\tt \huge \implies \:a _ { 2 0} = 7 + (20 - 1)3 \\ \\ \tt \huge \implies \:a _ { 2 0} = 7 + (19)3 \\ \\ \tt \huge \implies \:a _ { 2 0} = 7 + 57 \\ \\\tt \huge \implies \:a _ { 2 0} = 64$

20 th term of AP is 64....