An important question from ML Agarwal (avichal publication) If sum of the 3rd and 8th term of an ap is 7 and the sum of the 7th and 14th term is -3.find the 10th term.
ML Publication, Class 10, Arithmetic Progression Chapter 9, question no. 16
Rajan@2021Guru
If sum of the 3rd and 8th term of an ap is 7 and the sum of the 7th and 14th term is -3.find the 10th term
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nth term tn=a+(n−1)d
a= First term
d= Common difference
n= number of terms
tn=nth term
a3+a8=7a+2d+a+7d
=72a+9d=7⟶(i)
a7+a14
=−3a+6d+a+13d
=−32a+19d=−3⟶(ii)
From (i) & (ii)
2a+9d=72a+19d=−3
−10d=10d=−1,a=8.
a10=a+9d=8+9(−1)=−1