Find the discriminant of the polynomial below.
9x^2-18x+9

Question

Find the discriminant of the polynomial below.
9x^2-18x+9

anonymous · Answer

648

anonymous · Answer

$$-18^{2}-4(9)(9)=-324-324=648$$

anonymous · Answer

$$take \left( -18 \right)^{2}=324$$

anonymous · Answer

so 0

anonymous · Answer

so it is 324-324=0

mathstudent55 · Answer

$b^2 - 4ac =$

$= (-18)^2 - 4( 9)(9) $

$= 324 - 324 $

$= 0$

mathstudent55 · Answer

You need to be careful with this:

If a = 5, then you know that a^2 = 5^2 = 25. That's simple.

Here's where you need to be careful.
If a = -5, then a^2 = (-5)^2 = 25. You must have the parentheses around -5. This is correct.

The following line is incorrect:
If a = -5, then a^2 = -5^2 = -25.

In math, (-5)^2 means (-5)(-5) = 25.
In math, -5^2 means -(5)(5) = -25.
If you have a = -5, and you need to find a^2, you need to do (-5)^2 which means (-5)(-5) which equals positive 25, since it is the product of 2 negative numbers.
If you incorrectly state that if a = -5, then a^2 = -5^2, then you'll get -25 which is incorrect.