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Polynomial Division. Objective: To divide polynomials by long division and synthetic division. What you should learn. How to use long division to divide polynomials by other polynomials How to use synthetic division to divide polynomials by binomials of the form ( x – k )
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Polynomial Division Objective: To divide polynomials by long division and synthetic division
What you should learn • How to use long division to divide polynomials by other polynomials • How to use synthetic division to divide polynomials by binomials of the form (x – k) • How to use the Remainder Theorem and the Factor Theorem
x2 times. 1. x goes into x3? 2. Multiply (x-1) by x2. 3. Change sign, Add. 4. Bring down 4x. 5. x goes into 2x2? 2xtimes. 6. Multiply (x-1) by 2x. 7. Change sign, Add 8. Bring down -6. 9. x goes into 6x? 6times. 10. Multiply (x-1) by 6. 11. Change sign, Add .
Long Division. Check
Long Division. Check
Example = Check
The Division Algorithm If f(x) and d(x) are polynomials such that d(x)≠ 0, and the degree of d(x) is less than or equal to the degree of f(x), there exists a unique polynomials q(x) and r(x) such that Where r(x) = 0 or the degree of r(x) is less than the degree of d(x).
Synthetic Division Divide x4 – 10x2 – 2x + 4 by x + 3 1 0 -10 -2 4 -3 -3 +9 -3 3 -1 1 1 1 -3
Long Division. 1 -2 -8 3 3 3 -5 1 1
The Remainder Theorem If a polynomial f(x) is divided by x – k, the remainder is r = f(k).
The Factor Theorem A polynomial f(x) has a factor (x – k) if and only if f(k) = 0. Show that (x – 2) and (x + 3) are factors of f(x) = 2x4 + 7x3 – 4x2 – 27x – 18 2 7 -4 -27 -18 +2 4 22 18 36 9 0 2 11 18
Example 6 continued 2 7 -4 -27 -18 +2 Show that (x – 2) and (x + 3) are factors of f(x) = 2x4 + 7x3 – 4x2 – 27x – 18 4 22 18 36 9 -3 2 11 18 -6 -15 -9 0 2 5 3
Uses of the Remainder in Synthetic Division The remainder r, obtained in synthetic division of f(x) by (x – k), provides the following information. • r = f(k) • If r = 0 then (x – k) is a factor of f(x). • If r = 0 then (k, 0) is an x intercept of the graph of f.