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lily
12-26-2013, 09:16 AM
Which of the following is equal to the number of roots having the quadratic equation x^2+4x+4=0?

(A) 0
(B) 1
(C) 2
(D) -2
(E) -1

Thanks!

miranda
12-27-2013, 05:35 AM
Which of the following is equal to the number of roots having the quadratic equation x^2+4x+4=0?

(A) 0
(B) 1
(C) 2
(D) -2
(E) -1

Thanks!

This is an easy SAT question using GDC and find the roots of the given quadratic equation.
Another way is to recognize the identity x^2+4x+4=(x+2)^2 and thus the equation has one double (repeated) root.
One more way to find the correct answer is to calculate the discriminant \delta=b^2-4ac=4^2-4\cdot4=0, therefore the equation has only one double root.
Therefore the correct answer is (B).