finding the x intercept of this here parabola: y=-1- x^2

0=-1- x^2

1= -x^2

I know the x intercepts are (1,0);(-1,0) but I don't know how. To square root it, do I change the 1 to a negative or can I take out the negative sign altogether since it's x squared, or would that alter the equation altogether if I ever wanted to do some higher level shit to this thing?

and thanks to the answerer!

You have to factor

y = 1 - x^2

0 = 1 - x^2

x^2-1

(x+1)(x-1)

Then from here

x+1=0 x-1=0

x=-1 x=1

There are no real solutions to the equation 0 = -1 - x^2, try graphing y = -x^2 - 1 to see why. Allowing imaginary solutions, the solutions are i and -i.

Shadout has it right, I fucked up the equation. Miss one negative and everything is wrong.

Going from where you had it:

1 = -x^2

-1 = x^2 divide by -1

plus or minus sqrt-1 = x Square root

i,-i = x

ehhh I was hoping I didn't have to resort to imaginary numbers.


thanks you guys

look at the function.

-x^2 means it concaves downwards. -1 means the y intercept is at -1.

if you draw this, the parabola would not touch the x-axis, so there are no real solutions

also, to check this, use the discriminant (the bit in the square root of the quadratic formula)

b^2-4ac

in y=-1-x^2
a=-1
b=0
c=-1

0^2-4*-1*-1 = -4 < 0

because its negative, it has no real solutions
if the discriminant =0, there is one solution, if it is >0 there are 2 solutions

If you're in calculus this year, I'd suggest getting Maple as a study tool.

It'll help when your teacher gives you THIS (http://commons.wikimedia.org/wiki/Image:Trident_de_Newton.png) or something equally fucked up and wants to find certain values.

omg i really hate maple. At university, using it actually forms 8% of our marks for maths, and i really suck at it.

Though OP, if you do learn maple, it can be really good for solving assignments