Find the respective terms for the following APs.
a2 = 13, a4 = 3, find a1, a3
Given that a2 = 13 & a4 = 3
a2 = a1 + (2-1)d
13 = a1 + d ⇒ 1
a4 = a1 + (4-1)d
3 = a1 + 3d ⇒ 2
By subtracting the both equations
13 – 3 = (a1 + d ) - (a1 + 3d)
10 = -2d
d = -5
By substituting in 1 equations we get a1
13 = a1 + (-5)
18 = a1
a3 = a1 + (3-1)d
= 18 + 2 × (-5)
= 8.
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