elizabeth

10-19-2013, 05:57 PM

If x^2-4x>0, then which one of the following could NOT be the value of x ?

(A) -2

(B) -1

(C) 1

(D) 5

Thanks!!;)

(A) -2

(B) -1

(C) 1

(D) 5

Thanks!!;)

View Full Version : sat math inequality question

elizabeth

10-19-2013, 05:57 PM

If x^2-4x>0, then which one of the following could NOT be the value of x ?

(A) -2

(B) -1

(C) 1

(D) 5

Thanks!!;)

(A) -2

(B) -1

(C) 1

(D) 5

Thanks!!;)

kadence

10-19-2013, 05:57 PM

Solving the following inequality for x

x^2-4x>0

x(x-4)>0

Inserting the roots 0, 4 in the number line below and starting from the right with + since the leading coefficient is positive, we have the following sign diagram.

---(+)--------{0}---------(-)-------------{4}-------(+)---------

So, the inequality holds for x<0 and x>4 and the only value from (A)-(D) which is between 0 and 4 is the value of 1.

Therefore the correct answer is (C).

x^2-4x>0

x(x-4)>0

Inserting the roots 0, 4 in the number line below and starting from the right with + since the leading coefficient is positive, we have the following sign diagram.

---(+)--------{0}---------(-)-------------{4}-------(+)---------

So, the inequality holds for x<0 and x>4 and the only value from (A)-(D) which is between 0 and 4 is the value of 1.

Therefore the correct answer is (C).

elizabeth

10-19-2013, 05:58 PM

Thanks Kadence!!

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