Question

The sum of 5th and 7th terms of an AP is 4 and the tenth term is forty six .find the ap

Answer 1

Solution:-

Given : Sum of the 5th and 7th term is 4.

∴ a + 4d + a + 6d = 4

2a + 10d = 4...............(1)

Also given : 10th term is 46

∴ a + 9d = 46

Multiplying it by 2, we get

2a + 18d = 92 ................(2)

Now, subtracting equation (1) from equation (2), we get.

Now solve... :-)

Answer 2

given

sum of 5th and 7th terms of an AP is 4

the tenth term is forty six

here we already know that an=a+(n-1)d

sum of 5th and 7th terms

=a+4d+a+6d = 4

=2a+10d = 4

dividing whole equation with 2

= a+5d = 2 eq---(1)

the tenth term is forty six

=a+9d = 46 eq-----(2)

by subtracting 1 and 2

we get

a+5d = 2

(-)a+9d = 46

___________

a+5d = 2

-a-9d = -46

__________

-4d = -44

d = 11

__________

therefore d = 11

substituting d=11 in eq----(1)

= a+5(11) = 2

a = 2-55

a=-53

therefore the ap is -53, -42, -31...........so on

hope its helpful #hard#work...

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