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3/11/2013 2:51:19 AM
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Algebra help

Stuck on this last piece of my homework and it's messing with my mind, a lot. I know there are many math enthusiasts on here or just generally the intellect is very high, so I figured I'd ask here, help of course is highly appreciated. f(x) = 6x^3 + px^2 + qx + 8 where p and q are constants. Given that f(x) is exactly divisible by (2x-1), and also that when f(x) is divided by (x-1) the remainder is -7 a) find the value of p and the value of q

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  • We could do long division on this to figure stuff out. Start off with the x-1, I get the feeling it will give us immediate results. x goes into 6x^3 6x^2 times. This leaves us with a remainder of (p-6)x^2 + qx + 8. x goes into (p-6)x^2 (p-6)x times. This leaves us witha remainder of (q-p+6)x + 8. x goes into (q-p+6)x (q-p+6) times. This leaves us with a remainder of (8 - q + p - 6) = (2 - q + p). x does not go into (2 - q + p), so we are done here. The problem tells us that our remainder should equal -7. So -7 = (2 - q + p) We do long division a second time, this time with (2x-1). 2x goes into 6x^3 3x^2 times, which leaves us with a remainder of (p-3)x^2 + qx + 8. 2x goes into (p-3)x^2 ((p-3)/2)x times, which leaves us with a remainder of (q - ((p-3)/2))x + 8. 2x goes into (q - ((p-3)/2))x (q - ((p-3)/2))/2 times, which leaves us with a remainder of 8 - (q - ((p-3)/2))/2 The problem says that it is exactly divisible by (2x-1), so the remainder should actually equal zero. So 0 = 8 - (q - ((p-3)/2))/2 We now have a system of equations, and you should be able to solve for q in terms of p or p in terms of q in one or the other, substitute it into the other equation, and find the answer. Does that make sense?

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