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anonymous

  • one year ago

Paula used synthetic division to divide the polynomial f(x) by x + 1, as shown: What is the value of f(–1)? 7 –2 1 –1

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  1. anonymous
    • one year ago
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  2. zepdrix
    • one year ago
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    Sorry I had to read up a sec :) I sort of forgot synthetic lol The Remainder Theorem tells us that when you perform this division, the remainder will tell us the value of the function at that x value. Do you know how to find the remainder in this division diagram?

  3. anonymous
    • one year ago
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    think about what you compute using synthetic division: $$(-2\cdot-1+-5)\cdot-1+4=-2\cdot(-1)^2-5\cdot(-1)+4=-2x^2-5x+4$$ evaluated at \(x=-1\)

  4. anonymous
    • one year ago
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    the remainder (final) term in synthetic division gives you the value of the polynomial at that point; see the remainder theorem -- if we divide a polynomial \(P\) by a divisor \(D\) and get the quotient \(Q\) with remainder \(R\) we have: $$P(x)=D(x)Q(x)+R(x)$$ if \(D\) has a zero at \(x=a\), then we see: $$P(a)=D(a)Q(a)+R(a)\\\implies P(a)=R(a)\text{ since }D(a)=0$$ so if we divide by a monomial \(D(x)=x+1\), the remainder \(R(x)\) will tell us the value at the zero of \(D\) (which is \(-1\), since \(D(-1)=0\)). see: $$P(-1)=D(-1)Q(-1)+R(-1)\\\implies P(-1)=R(-1)$$ so the remainder term givesu s what we want

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