Tip:A–D to answerE for explanationV for videoS to reveal answer
If an=4n2−16n+15−2, then a1+a2+...+a25 is equal to:
- A.
14752
- B.
13849
- C.
14150
Explanation
Solution:
an=(2n−3)(2n−5)−2=2n−31−2n−51
∑n=125an=(−11−−31)+(11−−11)+...+(471−451)
Telescopic sum: 471−−31=471+31=14150
Correct Option: (3)
Explanation
Solution:
an=(2n−3)(2n−5)−2=2n−31−2n−51
∑n=125an=(−11−−31)+(11−−11)+...+(471−451)
Telescopic sum: 471−−31=471+31=14150
Correct Option: (3)
