Question

Choose the correct answer from the given four options:The 21st term of the AP whose first two terms are –3 and 4 is

17

-137

137

127​

Answer 1

B) -137

Explanation:

a=a1=−3,a2=4

∴d=a2−a1=4−(−3)=4+3=7

Answer 2

137

Explanation:

given AP

t1 = -3 and t2 = 4

using,

d=t1-t2

=4-(-3)

=7

And,

tn=a+(n-1)d

t21=(-3)+(21-1)(7)

t21=137