Which expression is a factor of 9r^2-4r+1

There are no real factors for this.

Step-by-step explanation:

We could answer this either by checking each listed expression to see whether it is a factor of 9r^2-4r+1, or

We could take the coefficients of 9r^2-4r+1, determine the quantity b²-4ac (called the 'discriminant') and draw a conclusion based upon whether the discriminant is -, + or 0.

Let's use the 2nd approach.

Here, a = 9, b = -4 and c = 1.

Then the discriminant is b²2 - 4ac, or (-4)² - 4(9)(1), or 16 - 36.

Since 16 - 36 is negative, we conclude that this 9r^2 - 4r + 1 has NO REAL FACTORS.

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step-by-step explanation: