Question

If 4 times the 4th term of an A.P. is equal to 9 times the 9th term of the A.P., what is 13 times the 13th term of this ?

Answer 1

ANSWER- 13(t13) = 0

EXPLANATION

4(t4)=9(t9)

4(a+3d)=9(a+8d)

4a+12d= 9a+ 72d

4a-9a= 72d-12d

-5a=60d

$\frac{a}{d} = \frac{60}{ - 5}$

hence, a=60. d=-5

t13= a+(n-1)d

t13= 60+ 12× -5

t13= 60+ (-60)

t13= 60-60

t13=0

13(t13)= 0×13

13(t13)=0

hope this helps you

:-)