the sum of 3rd and 7th term of an ap is 6 and their product is 8 find the first term and the common difference of the AP
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Here ,According to the question
a3+a7=6 1st eq.
and
a3×a7=8 2nd eq.
a3=a+2d
a7=a+6d
putting values of these we get
a+2d+a+6d=6
2a+8d=6
2(a+4d)=2(3)
a+4d=3
a=3-4d 3rd eq.
also we can write 2nd eq. as
(a+2d)×(a+6d)=8
putting value of a from eq.3 we get
(3-4d+2d)×(3-4d+6d)=8
solving it further
(3-2d)(3+2d)=8
3^2-(2d)^2=8
9-4d^2=8
-4d^2=-1
d^2=1/4
d=+1/2 and -1/2
that's your answer
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Jeetmanjrekar:
Good correct answer
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