Big Ideas Math Algebra 2, 2014
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Big Ideas Math Algebra 2, 2014 View details
3. Dividing Polynomials
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Exercise 36 Page 178

The Remainder Theorem states that if a polynomial f(x) is divided by x-k, then the remainder is f(k).

See solution.

Practice makes perfect

Let's start by recalling the The Remainder Theorem.

If a polynomial function f(x) is divided by x-k, then the remainder is f(k).

The Remainder Theorem tells us that we can find the value of the polynomial function at x=k by dividing it by the binomial x-k. This allows us to evaluate the polynomial using synthetic division. Consider the given function. P(x) = - 6x^3+72x This function gives us the profit P in millions of dollars for a DVD manufacturer when x millions of DVDs are produced. According to the Remainder Theorem, we can find P(2) by dividing P(x) by x-2. Let's do this using synthetic division. Recall that we need to use a 0 for every missing x-term in the dividend polynomial.

rl IR-0.15cm r 2 & |rr -6 &0 &72 &0

Bring down the first coefficient

rl IR-0.15cm r 2 & |rr -6 &0 &72 &0 &&& & c -6 & & &

Multiply the coefficient by the divisor

rl IR-0.15cm r 2 & |rr -6 &0 &72 &0 &- 12&& & c -6 & & &

Add down

rl IR-0.15cm r 2 & |rr -6 &0 &72 &0 &- 12&& & c - 6 &- 12 & &
â–¼
Repeat the process for all the coefficients

Multiply the coefficient by the divisor

rl IR-0.15cm r 2 & |rr -6 &0 &72 &0 &- 12&- 24& & c - 6 & - 12 & &

Add down

rl IR-0.15cm r 2 & |rr -6 &0 &72 &0 &- 12&- 24& & c - 6 &- 12 & 48 &

Multiply the coefficient by the divisor

rl IR-0.15cm r 2 & |rr -6 &0 &72 &0 &- 12&- 24&96 & c - 6 &- 12 & 48 &

Add down

rl IR-0.15cm r 2 & |rr -6 &0 &72 &0 &- 12&- 24&96 & c - 6 &- 12 & 48 & 96

Since the remainder is 96, we know that P(2)=96. This means that when 2 million DVDs are produced, the company earns $96 million. Recall that we can also find this value by evaluating the function.

P(x) = -6x^3+72x
P( 2) = -6( 2)^3+72( 2)
â–¼
Simplify right-hand side
P(2) = -6(8)+72(2)
P(2) = -48+144
P(2) = 96

As we can see, evaluating the function is easier for this case.