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### How to determine the number of unique real roots of a quadratic equation.

Take any quadratic equation, eg/ 3x2+4x-2=5, and rearrange to equal 0, ie/ 3x2+4x-7=0   (if you have an expression, ie/ there is no equals sign, then simply equate the expression to 0).

Now, we use the discriminant function, b2-4ac, of the quadratic, ax2+bx+c=0. Notice that a=3, b=4, and c=-7, in this case. This means that the discriminant is 42-4*3*(-7)=16-(-84)=100. This is greater than 0. Therefore, there exist 2 unique real roots to our quadratic.

Simply put, if, for any quadratic of the form ax2+bx+c=0, that b2-4ac>0, then there exist 2 unique real roots, if b2-4ac=0 then there is 1 repeated real root, and if b2-4ac<0, then there are no real roots.

2 years ago

Answered by Yaniv, a GCSE Maths tutor with MyTutor

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