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Which one of these is quadratic? A) `y=x^2+3x` B)  `f(x) = x (4-x)-3` C) `3x^2-2=5x`

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babylove12 | Student, Grade 10 | (Level 3) eNoter

Posted June 30, 2013 at 4:32 PM via web

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Which one of these is quadratic?

A) `y=x^2+3x`

B)  `f(x) = x (4-x)-3`

C) `3x^2-2=5x`

4 Answers | Add Yours

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llltkl | College Teacher | (Level 3) Valedictorian

Posted June 30, 2013 at 4:51 PM (Answer #1)

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A quadratic equation in x is an equation that can be written in the general form:

`ax^2+bx+c=0`

where, a, b and c are real numbers with ‘a’ having a non-zero value.

A quadratic equation is also defined as a univariate polynomial equation of the second degree.

Options A) and B) contains equations that are not univariate, hence these two do not represent quadratic equations.

The equation in option C) is `3x^2-2=5x`

Which can be rewritten as:

`3x^2-5x-2=0`

This is definitely a quadratic equation, in x.

Thus, the correct answer is option C).

Sources:

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atyourservice | Student, Grade 10 | (Level 3) Valedictorian

Posted March 22, 2014 at 5:27 PM (Answer #2)

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c. because it has an a,b and c

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givingiswinning | Student, Grade 10 | (Level 1) Valedictorian

Posted July 31, 2014 at 11:21 AM (Answer #3)

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c. 

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taangerine | Student, Grade 11 | (Level 1) Valedictorian

Posted August 16, 2014 at 12:06 AM (Answer #4)

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A quadratic is essentially ax^2+bx+c. 

And, only choice C has those characteristics. 

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