# Discriminant

• Jan 10th 2007, 02:01 PM
symmetry
Discriminant
Use the discriminant to determine whether each quadratic equation has two unequal real solutions, a repeated real solution, or no solution, WITHOUT solving each equation below.

(1) x^2 + 5x + 7 = 0

(2) 2x^2 - 3x + 4 = 0

NOTE: What is the correct definition of a discriminant?
• Jan 10th 2007, 02:34 PM
galactus
Check the discriminant, as it says. If it's positive, then you have 2 unequal real roots. If it's negative, no real roots. If it's 0, one root of multiplicity 2.

$b^{2}-4ac$
• Jan 10th 2007, 04:49 PM
symmetry
ok
I simply plug the value of a, b and c as found in each equation into the discriminant, right?

Afterward, I simplify, right?
• Jan 10th 2007, 11:21 PM
earboth
Quote:

Originally Posted by symmetry
I simply plug the value of a, b and c as found in each equation into the discriminant, right?

Afterward, I simplify, right?

Hello,

that's 100% correct.

a = 1
b = 5
c = 7
Thus the discriminant d = 5²-4*1*7=-3. Therefore there exists no real solution.

EB
• Jan 11th 2007, 03:39 AM
symmetry
ok
Earboth,

Boy, this is very easy stuff. The question itself is not clear when first read but none the less very easy to handle.

Thanks!