Question

if 1+2+3........n terms =28 then n is
equal to
​

Answer 1

Answer:

22

Step-by-step explanation:

1+2+3+n(22)

so, the answer is 22

Answer 2

The value of n is 7

Step-by-step explanation:

To find: the value of n for which 1+2+3+............n=28

Now as we know

for n natural numbers  the sum of n natural number is given by

$1+2+3+4+..........................+n= \dfrac{n(n+1)}{2}$

As given the sum id 28

so we have

$\dfrac{n(n+1)}{2} =28\\\\\Rightarrow n^2+n=56\\\\\Rightarrow n^2+n-56=0$

Now by middle term split method we get

$\\\\\Rightarrow n^2+8n-7n-56=0\\\\\Rightarrow n(n+8)-7(n+8)=0\\\\\Rightarrow (n-7)(n+8)=0$

Now if a.b=0 then either a=0 or b=0

Therefore

n=7   or n=-8(rejected as natural number can't be negative)

Hence, the value of n is 7

#Learn more

Sum of 1st 30 natural numbers?

brainly.in/question/7566432