# Math Help - graphing equations...

1. ## graphing equations...

I am asked to graph this equation by plotting points;

$y=-x^2+4$

So far I have used these numbers to get the value of $y$

x=0 y=4

x=1 y=5

x=2 y=8

But the problem I am having is that if I keep on, the value for $y$ gets further away from the first two points.

If I use a negative number it obviously becomes a positive number....

Could I multiply the entire equation by $-1$ so that the $4$ becomes a negative?

Many thanks in advance

BTW, how do I create a space between the numbers so that when I post it doesn't look too awkward, or confusing??!??

2. Originally Posted by Morzilla
I am asked to graph this equation by plotting points;

$y=-x^2+4$

So far I have used these numbers to get the value of $y$

x=0 y=4

x=1 y=5

x=2 y=8

But the problem I am having is that if I keep on, the value for $y$ gets further away from the first two points.

If I use a negative number it obviously becomes a positive number....

Could I multiply the entire equation by $-1$ so that the $4$ becomes a negative?

Many thanks in advance
first off, your points are wrong. when the minus sign is outside the x^2, the answer is negative. there is a difference between $-x^2$ and $(-x)^2$. you were doing the latter, when the first is what is meant

the points x = -2, -1, 0, 1, 2 are fine

BTW, how do I create a space between the numbers so that when I post it doesn't look too awkward, or confusing??!??
i don't know what you're referring to

3. Originally Posted by Jhevon
first off, your points are wrong. when the minus sign is outside the x^2, the answer is negative. there is a difference between $-x^2$ and $(-x)^2$. you were doing the latter, when the first is what is meant

the points x = -2, -1, 0, 1, 2 are fine

i don't know what you're referring to
but wait, if I where to give $-x^2$ a value; $-x^2$= $-2^2$, would it not be 4, since two to the second power is four!?

thanks

4. Originally Posted by Morzilla
but wait, if I where to give $-x^2$ a value; $-x^2$= $-2^2$, would it not be 4, since two to the second power is four!?

thanks
no. the answer would be -4. the minus sign is on the outside of the square, meaning, it is not affected by the squaring. the squaring only affects the x here

now let's say we had x^2, and we plug in x = -2, then we would have (-2)^2 = +4. do you see the difference? the minus sign is in the brackets, so it is affected by the square

5. Originally Posted by Jhevon
no. the answer would be -4. the minus sign is on the outside of the square, meaning, it is not affected by the squaring. the squaring only affects the x here

now let's say we had x^2, and we plug in x = -2, then we would have (-2)^2 = +4. do you see the difference? the minus sign is in the brackets, so it is affected by the square

So ,it does not matter what number we plug in -x^2, the number will still be a negative number then?

6. Originally Posted by Morzilla
So ,it does not matter what number we plug in -x^2, the number will still be a negative number then?

correct, because x^2 will always be non-negative, but the minus sign in front negates it, so you end up with a non-positive number

7. ahhhhh, ok THANK YOU THANK YOU VERY MUCH!!!!