# Homework Help: Algebra II

1. Mar 29, 2006

### Joebird

I'm supposed to use this equation:

y = x^2-8x+7

To solve the following questions:

1) What is the value of the discriminant?
2) Find the roots by factoring and solving.
3) Find the roots by using the quadratic equation.

Can anyone give me some help?

Thanks! :)

2. Mar 29, 2006

### JasonRox

Do you know what the discriminant is?

Do you know how to factor?

Do you know what the quadratic equation is?

http://home.alltel.net/okrebs/page6.html [Broken]

Here's a link if you don't feel like searching.

Last edited by a moderator: May 2, 2017
3. Mar 29, 2006

### JasonRox

Is this really Algebra II?

4. Mar 29, 2006

### Joebird

Tryed myself, the discriminant is "x^2 - 8x"?

The factor is: (x - 7)(x - 1) But are those the roots also?

Thanks for the help! :)

PS: Yes, this is in my Algebra II class.

5. Mar 29, 2006

### JasonRox

6. Mar 29, 2006

### HallsofIvy

Do you know the quadratic formula? I'll bet it's in your book. I'll also bet they define "discriminant" in the same section. (No, it's not "x^2- 8x". The discriminant is a number not an expression in x.)

7. Mar 29, 2006

### JasonRox

Why look in the book when people online will answer it? :uhh:

8. Mar 29, 2006

### Joebird

It probably is in my book, but I'm sick and my book was left in my locker as I thought I was going to school today. I'm looking it up on how to do it, although I can find examples I can't figure out how they change it.

Thanks :)

PS: The roots are x = {7,1} I believe?

9. Mar 29, 2006

### Joebird

{-8 ± Sq Root (64 - 28)} ÷ 2

That means the discriminant is:

64 - 28

I hope thats right.

Thanks!

10. Mar 29, 2006

### Joebird

Thanks for all the help. :)

On the question:

Find the roots by using the quadratic equation.

Would the answer be x = {7,14}?

Thanks :)

11. Mar 29, 2006

Substitute your answers in the original equation. You'll see immediately if they're correct.

12. Mar 29, 2006

### Joebird

Okay, thanks. :)

How would I find the 'x =' in the equation? (y = x^2-8x+7)

THANKS! :)

13. Mar 29, 2006

### Tom Mattson

Staff Emeritus
High school and college level homework goes into the Science Education Zone, please.

You have to show some work first.

14. Mar 29, 2006

### JasonRox

Hint: Take a closer look at the Quadratic Formula.

15. Mar 30, 2006

### HallsofIvy

The quadratic formula is "overkill" for this one. How can you factor 7?

Edit: I just noticed, this is not x^2- 8x+ 7= 0, which would give x= 7, x= 1 as roots, but y= x^2 - 8x+ 7. To solve that for x, in terms of y, you would need to use the quadratic formula (or complete the square).

Last edited by a moderator: Mar 31, 2006
16. Mar 30, 2006

### konartist

discriminant = #'s inside the radical.

to solve the factoring problem you must know :
F-irst
O-utside
I-nside
L-ast

For example if we had $$x^2+7x+12=0$$ we would factor it light this
$$(x+3)(x+4)$$

To know if you have done your work right use FOIL
First: $$x \times x$$
Outside: $$4 \times x$$
Inside: $$3 \times x$$
Last: $$3 \times 4$$

To find the zeros (or answers) of x for : $$(x+3)(x+4)$$ we would simply take:
$$(x+3)=0$$ and solve for x and $$(x+4)=0$$