Question

Determin the AP whose 5th term is 15 and sum of it's 3 and 8th term is 34
Plz answer fast

Answer 1

Heya!!

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Since a(n) = a + (n-1)d

=) a5 = a + 4d = 15 :.. Eq1.

A/Q : a3 + a8 = 34

=) a+2d + a+7d = 34

=) 2a + 9d = 34 .. Eq2.

Multiply eq1 by 2;

=) 2a+ 8d = 30 .. Eq3.

Subt :

=) d = 4

Put value of d in eq1

=) a+ 16 = 15

=) a = - 1

Hence AP is - 1, 3, 7, 11....
Hope it helps uh

Answer 2

hey mate!

5th =a+4d=15
and 3rd + 8th=34
a+2d+a+7d=34
=2a+9d=34

a+4d=15
a=15-4d


now, 2(15-4d)+9d=34
30-8d+9d=34
d=34-30
d=4

a=15-4d
a=15-4(4)
a=15-16=-1


so, AP is -1,-1+4=3,-1+2(4)=7

that is -1,3,7,11..........


hope it helps!!