KJ4UTS
  • KJ4UTS
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
Mathematics
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SOLVED
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katieb
  • katieb
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Nnesha
  • Nnesha
what is discriminant ? do you know ?
KJ4UTS
  • 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
KJ4UTS
  • KJ4UTS
b^2-4ac

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KJ4UTS
  • KJ4UTS
x^2-5x-7=0 2 roots x^2-2x+1=0 1 root
Nnesha
  • 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)
Nnesha
  • Nnesha
you should use discriminant
Nnesha
  • Nnesha
ohh wait nmv
Nnesha
  • 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)
Nnesha
  • Nnesha
so (-2)^2 -4 = ?
KJ4UTS
  • KJ4UTS
-8
Nnesha
  • Nnesha
no (-2)^2 is same as -2 times -2
Nnesha
  • Nnesha
or in other words when you take `even` power of negative exponent you will get positive answer always !
KJ4UTS
  • KJ4UTS
0
Nnesha
  • Nnesha
no \[\color{ReD}{(-2)^2}-4(1)(1)\] i'm just talkign about (-2)^2
Nnesha
  • Nnesha
talking *
Nnesha
  • Nnesha
yes right
Nnesha
  • 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 ?
KJ4UTS
  • KJ4UTS
x^2-2x+1=0 -2^2-4(1)(1)=0=0 Which would still be 1 root?
Nnesha
  • Nnesha
yes right
Nnesha
  • Nnesha
now what about first one ? b^2-4ac = ??
KJ4UTS
  • KJ4UTS
Was my work right -5^2-4(1)(-7)=3>0 2 roots
Nnesha
  • Nnesha
no that's not correct ....
KJ4UTS
  • KJ4UTS
53
KJ4UTS
  • 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?
Nnesha
  • Nnesha
yes right
KJ4UTS
  • KJ4UTS
Ok thank you @Nnesha for your time and help, and for also pointing out where I went wrong :)
Nnesha
  • Nnesha
np and yes you should put the parentheses (-2)^2 like this :=) good job!

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