#### Thank you for registering.

One of our academic counsellors will contact you within 1 working day.

Click to Chat

1800-5470-145

+91 7353221155

CART 0

• 0
MY CART (5)

Use Coupon: CART20 and get 20% off on all online Study Material

ITEM
DETAILS
MRP
DISCOUNT
FINAL PRICE
Total Price: Rs.

There are no items in this cart.
Continue Shopping

# f(x+y)=f(x)+f(y)...............∑ f(x)=84 (upto n terms......starting from x=1)...........f(1)=3.............then find n....PLS EXPLAIN THIS QUESTION >>>>.........

9 years ago

Dear Shivam,

f(x+y)=f(x)+f(y)  put x = y = 1      f(1) = 3

f(2) = 6

put   x= 1, y = 2

f(3) = 9

similarly f(4) = 12

so this is an A.P starting from 3  and the common difference is also 3

the

∑ f(x)=84   starting from 1 is the sum of first n terms

so by the formula

84 = n/2[2a + (n-1)d]

so putting the values we get the quadratic in n

n2 + n - 56 = 0

so solving we get the value of n = 7

Now you can win by answering the questions on Discussion Forum. So help discuss any query on askiitians forum and become an Elite Expert League askiitian.