Which expression is a factor of 9r^2-4r+1?
a)3r-1
b)r-1
c)9r-1
d)there are no real factors

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.

a box 3 3/4 feet long or 4+ feet.

step-by-step explanation: