If the 4th and the 9th terms of an AP are 5 and -5 respectively, which term of the AP is -15?
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Step-by-step explanation:
a4= a+3d = 5 ------------------>(1)
a9=a+8d = -5 ------------------>(2)
from eq (1)nd (2)
a+3d-a-8d = 5-(-5)
-5d = 10
d =-10/5
d = -2
therefore d = -2
substituting the value of d in eq (1)
a+3d=5
a+3(-2)=5
a-6=5
a=5+6
a=11
an=a+(n-1)d [here n will come below a]
-15=11+(n-1)-2
-15=11-2n+2
-15-13=-2n
-28=-2n
-28/-2=n
14=n
Therefore in 14th term the AP will be -15
hope it is helpful mark as brainlist
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