Help w/ sigma x^2 - (sigma x)^2/N, x = -1, 0, 4, -2, 3

[stanfieldmk]

So the expression is ?x^2-(?x)^2/N
the x values are as follows -1, 0, 4, -2, 3

I got the answer of 14/5 and i'm not sure if that is correct

for ?x^2 i got (-1)^2+0^2+4^2+(-2)^2+3^2 which equals 30

for (?x)^2 i got (-1+0+4+(-2)+3)^2= 4^2=16

30-16/5= 14/5

if you could help me determine what I did wrong
or if the answer is correct I would really appreciate it. Thanks.

 

[Loren]

Re: Help with problem

>So the equation is ?x^2-(?x)^2/N
the x values are as follows -1, 0, 4, -2, 3

First, that is not an equation. It is an expression. I agree with most of your work. But 30 - 16/5 is not 14/5.

 

[stanfieldmk]

Re: Help with problem

>So the equation is ?x^2-(?x)^2/N
the x values are as follows -1, 0, 4, -2, 3

First, that is not an equation. It is an expression. I agree with most of your work. But 30 - 16/5 is not 14/5.

oh sorry it is an expression
but i don't understand how it would not be 14/5
because isn't 30-16= 14?

the only other reasonable answer I can think of is 26.8
because i made 30/1 into 150/5 and subtracted 16/5 which came to 134/5= 26.8
this problem is really starting to confuse me...

 

[mmm4444bot]

REVIEW BASIC FRACTION ARITHMETIC

\(\displaystyle \frac{30 - 16}{5} = \frac{14}{5}\)

\(\displaystyle \frac{30}{1} - \frac{16}{5} =\) something else entirely

 

[Deleted member 4993]

Re: Help with problem

So the expression is ?x^2-(?x)^2/N
the x values are as follows -1, 0, 4, -2, 3


I got the answer of 14/5 and i'm not sure if that is correct

for ?x^2 i got (-1)^2+0^2+4^2+(-2)^2+3^2 which equals 30

for (?x)^2 i got (-1+0+4+(-2)+3)^2= 4^2=16

30-16/5= 14/5

You would be correct if your problem was:

[?x^2-(?x)^2]/N

Remember to use PEMDAS - order of operation.

as you wrote the problem

the answer would be 134/5

if you could help me determine what I did wrong
or if the answer is correct I would really appreciate it. Thanks.

 

[Loren]

Re: Help with problem

Seems to me you are just manipulating symbols rather than understanding the meaning of those symbols.

30-16/5= 14/5

What is the value of 16/5?

Does it make sense to say that \(\displaystyle 30 - 3\frac{1}{5} = 2\frac{4}{5}\) ?