how many term of an ap -6,-11/2,5needed togive the sum-25
Answers
Answered by
0
Answer:
5 terms will be required
Answered by
0
Answer:
20
Step-by-step explanation:
Let, the terms needed to give the sum -25 is X
∴ The 1st term of the AP series is = - 6 & the common difference is
= =
∴ According to the formula,
the sum of the X terms are = * (2 * (- 6) + (X - 1) * ) = -25
=> * (-12 + - ) = -25
=>
=> X (-25 + X) = -25 * 4
=> -25X + X² = -100
=> X² - 25X + 100 = 0
=> X² - 20X - 5X + 100 = 0
=> X * (X - 20) - 5 * (X - 20) = 0
=> (X - 5) * (X - 20) = 0
∴ X = 5 or, X = 20
∵ X ≠ 5
∴ X = 20
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