Question

I will fan and give medals!!! Please help!!!!

What is the discriminant for the quadratic expression?


18x2 + 11x


A.
49

B.
121

C.
193

D.
280

Answer 1

the discriminant is one of those expressions you have to memorize.
it's
\(\Huge b^2-4ac\)
in the quadratic expression
\(\Huge ax^2+bx+c\)
so if you find values for a, b, and c you can find the discriminant with substitution.

Answer 2

can you tell me what a, b, and c are in this expression?

Answer 3

i dont know

Answer 4

any ideas?

Answer 5

a=18x^2
b=11x

Answer 6

close...
a and b are really just the coefficients, or the numbers *in front* of the x's.
so a=18, and b=11
what about c?

Answer 7

i dont have idea

Answer 8

how about if I say
(18)x2 + (11)x + (0)?
that's the same thing as 18x2 + 11x right?

Answer 9

yes

Answer 10

so you want to find a, b, and c for
ax2+bx+c and you have
(18)x2 + (11)x + (0)
any guesses as to what c is?

Answer 11

ummmm.... no

Answer 12

look at the pattern: a is 18, and b is 11.
what does it look like c is?

Answer 13

7 ?

Answer 14

come on, don't guess. math is all about patterns, some of them easy, some of them hard.
I'll give you a hint: the answer is within the parenthesis...

Answer 15

I have no idea wahat it would be.......

Answer 16

here let me give you another hint:
(a) x2 + (b) x + (c)
(18)x2 + (11)x + (0)
if a is 18, and b is 11, what's c?

Answer 17

18+11=29

Answer 18

I'll tell you the pattern. a is the number in front of x2, which is 18. b is the number in front of x, which is 11. but there is no x for the third number, instead it's just c. so which number in the second row doesn't have an x after it?

Answer 19

still not sure

Answer 20

okay, here's c
(a) x2 + (b) x + (c)
(18)x2 + (11)x + (0)
if a is 18, and b is 11, then c is the last number in parenthesis, or 0.

Answer 21

what we need to do next is to find the value of the determinant,
which as I said earlier equals \(\large b^2-4ac\). All you have to do is substitute the values.
Can you do it?

Answer 22

ok i think i got it know

Answer 23

okay. I can check your answer with mine... let me know if you need anything else :)