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arun8408
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The series a1,a2,… is a geometric progression. If a4=80 and a5=160, what is the value of a1?
 one year ago
 one year ago
arun8408 Group Title
The series a1,a2,… is a geometric progression. If a4=80 and a5=160, what is the value of a1?
 one year ago
 one year ago

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agent0smith Group TitleBest ResponseYou've already chosen the best response.1
\[\large a _{n} = a _{1} r ^{n1} \] is the formula for a geometric progression, r being the common ratio, and a1 being the first term, an being the nth term. r is the common ratio, so if you divide a5 by a4, you'll find r. Then you can use \[\large a _{4} = 80 = a _{1} r ^{41}\] to find a1.
 one year ago

ParthKohli Group TitleBest ResponseYou've already chosen the best response.0
\[\dfrac{160}{80} = r\]
 one year ago

AravindG Group TitleBest ResponseYou've already chosen the best response.0
nth term of a GP= ar^{n1} use this and write the 5th and 4th terms ,you can solve them
 one year ago

ParthKohli Group TitleBest ResponseYou've already chosen the best response.0
\[r = 2\]You can now easily determine the first term by continuous division.
 one year ago

agent0smith Group TitleBest ResponseYou've already chosen the best response.1
You can find a1 by either just dividing by r until you reach a1, or using \[\large a _{4} = 80 = a _{1} r ^{41} \] \[\large a _{5} = 160 = a _{1} r ^{51} \]
 one year ago

arun8408 Group TitleBest ResponseYou've already chosen the best response.0
wat value do i substitute for r?
 one year ago

agent0smith Group TitleBest ResponseYou've already chosen the best response.1
\[\large r = \frac{ a _{5} }{ a _{4} }\]
 one year ago

arun8408 Group TitleBest ResponseYou've already chosen the best response.0
a1 . r^3 = a1 . 16??
 one year ago

agent0smith Group TitleBest ResponseYou've already chosen the best response.1
r should be 2, 160/80 = 2 \[\large a _{4} = 80 = a _{1} * 2 ^{41}\] \[\large 80 = a _{1}*2 ^{3}\]
 one year ago

arun8408 Group TitleBest ResponseYou've already chosen the best response.0
ya.. i got it.. 10 is d ans.. thank u so much
 one year ago

arun8408 Group TitleBest ResponseYou've already chosen the best response.0
What comes next in this sequence: 1,2,6,24,120,−−?
 one year ago

agent0smith Group TitleBest ResponseYou've already chosen the best response.1
There's a pattern: first term: 1x1 = 1 second term: 2x1 = 2 third term: 3x2 = 6 fourth term: 4x6 = 24 fifth term: 5x24 = 120 sixth term: ? x120 = ? Look at the pattern of multiples on the left.
 one year ago
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