The 4th term and the 19th term of an ap are -3 and 12 respectively. Find the common difference, 5th term and the number of terms which will give a sum of 135

Answer 1

Since the two given terms are 15 terms apart,
15d = 12 - (-3) = 15
d = 1
Now you have
T5 = t4 + d = -3 + 1 = -2
Now jsut figure a, and solve for n in
n/2 (2a + (n-1)d) = 135

Answer 2

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