Maths / Arithmetic Progression / Find Last Term When First Term, Number of Terms and Sum of N Terms is Given

QUESTION
 

Find the 6th term of an AP whose first trem  large 2x^2+2x-4 and sum of 6 terms is large 6x^2-x-4

 

OPTIONS
A. 

large frac{ -7x+8}{3}

B. 

large frac{ -7x+16}{3}

C. 

large frac{ -5x+8}{3}

D. 

large frac{ -5x-16}{3}

Right Option : A

EXPLANATION
Explain TypeExplanation Content
Text

large S_n = frac{n}{2}(a+l)

large 6x^2-x-4 = frac{6}{2}(2x^2+2x-4 +l)

large 6x^2-x-4 = 3(2x^2+2x-4 +l)

large 6x^2-x-4 = 6x^2+6x-12 +3l

large 3l = 6x^2-x-4 - 6x^2-6x+12

large 3l = -7x+8

large l =frac{ -7x+8}{3}

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