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What is the value of 5x^2 + 4x - 1 ? (1) x(x + 2) = 0 (2) x = 0 [#permalink]
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mashrur amin wrote:
How do we get x=0 from statement 1? Didn’t understand.

Posted from my mobile device


Statement 1: x(x + 2) = 0

For this to be true either x or (x+2) has to be 0
because 0 multiplied by any no. will give 0

If x=0 Statement becomes 0(0+2)= 0
If x=-2 Statement becomes -2(-2+2)= 0

Hope it helps.
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Re: What is the value of 5x^2 + 4x - 1 ? (1) x(x + 2) = 0 (2) x = 0 [#permalink]
What is the value of 5x^2 + 4x - 1 ?

(1) x(x + 2) = 0
We have two values of x 0 and -2.
We would get 2 values for the equation.
Insufficient.

(2) x = 0
We are directly provided for the value of x = 0
We get only one value for the equation.
Sufficient.

Note: We might in hurry give C as the solution as after combining we also get x = 0; but careful as statement 2 provides us the same information without combining. This is an example of C trap.
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Re: What is the value of 5x^2 + 4x - 1 ? (1) x(x + 2) = 0 (2) x = 0 [#permalink]
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Re: What is the value of 5x^2 + 4x - 1 ? (1) x(x + 2) = 0 (2) x = 0 [#permalink]
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