Question

If 5+7+9+......+x=320 then find value of x

Answer 1

Answer:a= 5

d= 7-5=2

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

or 320 = n/2 [2*5+(n-1)2]

or 320=n/2(10+2n-2)

or 320=n/2(2n+8)

Or 320= n(n+4)

Or 320 = n2+4n

Or n2+4n-320= 0

Or n2+20n-16n-320=0

Or n(n+20)-16(n+20)=0

Therefore n= 16(n cant be negative)

Now x is the 16th term

So a16= a+15d = 5+15*2=35

X = 35

Mark branliest plz

Answer 2

Given,

first term 'a' = 5

Common difference 'd' = 2

Sum of the series = 320

To find,

The value of x

Solution,

The value of x for is 35.

First-term 'a' =5

common difference 'd' = 2

Sum = 320

Sn = n/2 (2a+(n-1)d)

320 = n/2( 10 +(n-1)2)

320 = n(4+n)

320 = 4n +n²

n² +4n -320

(n-16)(n+20)

n=16

a16 =a+15d

      = 5+15(2)

      =35

Hence, the value of x is 35.