Question

If the sum of first 14th term of am Arithmetic progression is 10 and it's 1st term is 10. Find the 20th term​

Answer 1

Answer:

$\huge{\red{\boxed{\boxed{\green{\sf{a20=\frac{-120}{7}}}}}}}$

Step-by-step explanation:

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

□a1=10

□S14=10

To find:

○a20=?

$s14 = 10 \\ = ) \frac{n}{2} (2a + (n - 1)d) = 10 \\ = ) \frac{14}{2} (2 \times 10 + (14 - 1) \times d) = 10 \\ = )7(20 + 13d) = 10 \\ = )20 + 13d = \frac{10}{7} \\ = )13d= \frac{10}{7} - \frac{20}{1} \\ = )13d= \frac{10 - 140}{7} \\ = )13d = \frac{ -130}{7} \\ = ) d = \frac{ - 130}{7 \times 13} \\ = )d = \frac{ - 10}{7} \\ \\ a20 = a + 19d \\ = )10 + 19 \times \frac{ -10}{7} \\ = )10 + \frac{ - 190}{7} \\ = ) \frac{70 - 190}{7} \\ = ) \frac{ - 120}{7}$

$\huge{\red{\boxed{\boxed{\green{\sf{a20=\frac{-120}{7}}}}}}}$

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