Question

Use the discriminant to determine the number of real roots of...

x^2-5x-7=0

x^2-2x+1=0

Choices are:

0
1
2

Answer 1

what is discriminant ? do you know ?

Answer 2

Well my work is (I just want to check):

x^2-5x-7=0

-5^2-4(1)(-7)=3>0 2 roots

x^2-2x+1=0

-2^2-4(1)(1)=-8<0 1 root

Answer 3

b^2-4ac

Answer 4

x^2-5x-7=0

2 roots

x^2-2x+1=0

1 root

Answer 5

\(\huge\color{reD}{\rm b^2-4ac}\) `Discriminant`
you can use this to find if the equation is factorable or not
if ` b^2-4ac > 0` then there are 2 real zeros

if ` b^2-4ac = 0` then there is one real root
if ` b^2-4ac < 0` then you will get two complex roots (no -x-intercept)

Answer 6

you should use discriminant

Answer 7

ohh wait nmv

Answer 8

\(\color{blue}{\text{Originally Posted by}}\) @KJ4UTS
Well my work is (I just want to check):

x^2-5x-7=0

-5^2-4(1)(-7)=3>0 2 roots

x^2-2x+1=0

-2^2-4(1)(1)=-8<0 1 root
\(\color{blue}{\text{End of Quote}}\)
b^2 so it wohuld be (-2)^2 -4(1)(1)

Answer 9

so (-2)^2 -4 = ?

Answer 10

-8

Answer 11

no (-2)^2 is same as -2 times -2

Answer 12

or in other words when you take `even` power of negative exponent you will get positive answer always !

Answer 13

0

Answer 14

no \[\color{ReD}{(-2)^2}-4(1)(1)\] i'm just talkign about (-2)^2

Answer 15

talking *

Answer 16

yes right

Answer 17

\(\color{blue}{\text{Originally Posted by}}\) @Nnesha
\(\huge\color{reD}{\rm b^2-4ac}\) `Discriminant`
you can use this to find if the equation is factorable or not
if ` b^2-4ac > 0` then there are 2 real zeros

if ` b^2-4ac = 0` then there is one real root
if ` b^2-4ac < 0` then you will get two complex roots (no -x-intercept)
\(\color{blue}{\text{End of Quote}}\)
now read this when b^2-4ac =0 how many roots will u get ?

Answer 18

x^2-2x+1=0

-2^2-4(1)(1)=0=0

Which would still be 1 root?

Answer 19

yes right

Answer 20

now what about first one ?
b^2-4ac = ??

Answer 21

Was my work right -5^2-4(1)(-7)=3>0 2 roots

Answer 22

no that's not correct ....

Answer 23

53

Answer 24

I think what I was doing wrong for both was not putting parenthesis (-5)^2 for both problems into my calculator but 53>0 therefore I think it is still 2 roots?

Answer 25

yes right

Answer 26

Ok thank you @Nnesha for your time and help, and for also pointing out where I went wrong :)

Answer 27

np and yes you should put the parentheses (-2)^2 like this :=) good job!