# OH NO! A few problems

1. Mar 9, 2005

### valentines

see if any of you guys can solve a few of these.. if you guys can show me the steps so that i can study them for any of my future tests that would be great.

2. Mar 9, 2005

### The Bob

16. Do you know what a parabola is?? Do you know what a vertex is???

17. Can you complete the square???

18. This is more of trial and error than a formula.

19. Pretend the 'more than or equal to' sign is an equal sign and then solve.

20. Can you use the quadratic equation or factorise???

If you know any of this I can start to help, if not I need to explain it.

Last edited: Mar 9, 2005
3. Mar 9, 2005

### valentines

nope. i have no idea what im doing.

edit: actually, i know what a vertex is.

i dont know what a parabola is though

Last edited: Mar 9, 2005
4. Mar 9, 2005

### The Bob

A parabola is what you get when you draw the function y = x2. Do you know what that looks like???

Lets say you have x2 - 6x + 10. Completing the square would make the equation like this: (x - 3)2 + 10 - 9 = (x - 3)2 + 1. All that has happened is the -6x has been halved and put in brackets and then the new number (-3) has been squared and taken away from the 10.

Try completing the sqaure of x2 - 10x + 30. Completing the sqaure is also needed for 19.

18. I would use the quadratic forumla : $$\frac{-b \pm \sqrt{b^2 - 4ac}}{2a}$$ but I think it will want you to complete the square.

Question 20 can be factorise from 2x2 - 7x - 15 = 0 to (2x + 3)(x - 5) = 0 and then you have some values to use.

Last edited: Mar 9, 2005
5. Mar 9, 2005

### The Bob

I need to go sleep now but here are some completing the square question, for you, for practise and I am sure someone else will say if they are right or wrong for you:

y = x2 - 8x + 20
y = x2 - 4x + 7
y = x2 + 2x + 2
y = x2 + 4x + 2
y = x2 - 10x + 25

Good Luck and I will read what you have done tomorrow.