## KJ4UTS one year ago 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

1. Nnesha

what is discriminant ? do you know ?

2. 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

3. KJ4UTS

b^2-4ac

4. KJ4UTS

x^2-5x-7=0 2 roots x^2-2x+1=0 1 root

5. 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)

6. Nnesha

you should use discriminant

7. Nnesha

ohh wait nmv

8. Nnesha

$$\color{blue}{\text{Originally Posted by}}$$ @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)

9. Nnesha

so (-2)^2 -4 = ?

10. KJ4UTS

-8

11. Nnesha

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

12. Nnesha

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

13. KJ4UTS

0

14. Nnesha

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

15. Nnesha

talking *

16. Nnesha

yes right

17. Nnesha

$$\color{blue}{\text{Originally Posted by}}$$ @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 ?

18. KJ4UTS

x^2-2x+1=0 -2^2-4(1)(1)=0=0 Which would still be 1 root?

19. Nnesha

yes right

20. Nnesha

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

21. KJ4UTS

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

22. Nnesha

no that's not correct ....

23. KJ4UTS

53

24. KJ4UTS

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?

25. Nnesha

yes right

26. KJ4UTS

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

27. Nnesha

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