The 7th tern of ap is -4and 13th term -16 .find the A .P
Answers
As per question,
t7 = -4
a + 6d = -4 -------(1)
Again,
t13 = -16
a + 12d = -16 ------(2)
Subtracting (2)-(1)
a+ 12d = -16
-(a+6d) = -4
+ - +
___________
6d = -12
d = -2
Putting the value of 'd' in equation (1)
a + 6d = -4
a + 6(-2) = -4
a -12 = -4
a = -4+12
a = 8
Therefore,
A.P.
= a, a+d, a+2d..........
= 8, 6 , 4........
Answer:
A.P is 8,6,4,2,.......
Step-by-step explanation:
t7= -4 & t13= -16
using, tn = a+(n-1)d
t7 = a+(7-1)d
-4 = a+7d-d
-4 = a+6d
a+6d=-4...........(1)
similarly, tn = a+(n-1)d
t13 = a+(13-1)d
-16 = a+12d
a+12d = -16..........(2)
subtracting eq (1) from (2),
6d = -12
d = -2
substituting, d= 2 in eq (1),
a + 6(-2) = -4
a - 12 = -4
a = -4 +12
a = 8
a = -26 & d = 2
t1 = a = 8
t2 = t1 + d
= 8 + (-2)
t2 = 6
t3 = t2 + d = 6 - 2 = 4
t4 = t3 + d = 4 - 2 = 2
The sequence of A.P is 8,6,4,2,.........