lily

12-26-2013, 08:16 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!

(A) 0

(B) 1

(C) 2

(D) -2

(E) -1

Thanks!

View Full Version : SAT question Quadratic equation

lily

12-26-2013, 08:16 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!

(A) 0

(B) 1

(C) 2

(D) -2

(E) -1

Thanks!

miranda

12-27-2013, 04:35 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).

(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).

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