destroyer QR question

[IWantH2O]

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# 54....i dont know what the hell he is talkin bout here and have no clue how he got the answer....can someone please explain

 

[Streetwolf]

Post the Q.

 

[IWantH2O]

Post the Q.

which number is the discriminant of a quadratic equation whose roots are real unequal, and irrational?
a)0
b)-5
c)7
d)4
e)-9

 

[MattEvers]

Which number is the discriminant of a quadratic equation whose roots are real unequal and irrational.

0, -5, 7, 4, -9


The discriminant is the part under the square root in the quadratic equation.

Square root of a positive number gives you a real number, as apposed to a negative number giving an imaginary number. So you know the number is positive.

They are unequal, so it can't be zero since 0 and -0 are the same.

Finally, irrational numbers aren't whole numbers so any number whose square root is a whole number is also out (ie sqrt(4)=2).

So that only leaves 7.... hope that helps.