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Precalculus : Polynomial Functions

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Example Questions

Example Question #1 : Find Complex Zeros Of A Polynomial Using The Fundamental Theorem Of Algebra

The polynomial y = x^3 - x ^ 2 - x - 15 intersects the x-axis at point (3,0) . Find the other two solutions.

Possible Answers:

$1 \pm 4i$

$-1 \pm 2i$

$- 1 \pm 4i$

$-1 \pm 5 i$

$-2 \pm 4i$

Correct answer:

$-1 \pm 2i$

Explanation:

Since we know that one of the zeros of this polynomial is 3, we know that one of the factors is x - 3 . To find the other two zeros, we can divide the original polynomial by x - 3 , either with long division or with synthetic division:

$\begin{matrix} \underline{3}| \enspace 1 \enspace -1 \enspace -1 \enspace -15 \\\underline{ + \enspace \enspace \enspace \enspace 3 \enspace \enspace \enspace \enspace 6 \enspace \enspace \enspace 15 }\\ 1 \enspace \enspace \enspace 2 \enspace \enspace \enspace 5 \enspace \enspace \enspace 0 \end{matrix}$

This gives us the second factor of 1x^2 + 2 x + 5 . We can get our solutions by using the quadratic formula:

$\\x = \frac{-2 \pm \sqrt{4 - 4(1)(5)}}{2} \\ \\= \frac{-2 \pm \sqrt{ 4 - 20 }}{2 } \\ \\= \frac{-2 \pm \sqrt{-16}}{2} \\ \\= \frac{-2 \pm 4i }{2}\\ \\ = -1 \pm 2i$

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Example Question #1 : Find Complex Zeros Of A Polynomial Using The Fundamental Theorem Of Algebra

Find all the real and complex zeroes of the following equation: 2x^5+x^4-2x-1

Possible Answers:

$x=1, \frac{-1}{2}$

$x=1, -1, \frac{-1}{2}, \pm i$

$x=1, -1, \frac{-1}{2}, i$

$x=1,\frac{-1}{2}, i$

$x=1, \frac{-1}{2}, \pm i$

Correct answer:

$x=1, -1, \frac{-1}{2}, \pm i$

Explanation:

First, factorize the equation using grouping of common terms:

$2x^5+x^4-2x-1\rightarrow x^4(2x+1)-1(2x+1)\rightarrow (x^4-1)(2x+1)\rightarrow (x+1)(x-1)(x^2+1)(2x+1)$

Next, setting each expression in parenthesis equal to zero yields the answers.

$(x+1)=0\rightarrow x=-1$ $(x-1)=0\rightarrow x=1$ $(x^2+1)=0\rightarrow x=\pm i$

$(2x+1)=0\rightarrow x=\frac{-1}{2}$

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Example Question #1 : Find Complex Zeros Of A Polynomial Using The Fundamental Theorem Of Algebra

Find all the zeroes of the following equation and their multiplicity: g(t)=t^5-6t^3+9t

Possible Answers:

$t=0, \pm \sqrt{3i}$ (multiplicity of 2 on 0, multiplicity of 1 on $\pm \sqrt{3i}$

$t=0, \pm \sqrt{3i}$ (multiplicity of 1 on 0, multiplicity of 2 on $\pm \sqrt{3i}$

$t=0, \pm \sqrt{3}$ (multiplicity of 1 on 0, multiplicity of 2 on $\pm \sqrt{3}$

$t=0, \pm \sqrt{3}$ (multiplicity of 2 on 0, multiplicity of 1 on $\pm \sqrt{3}$

Correct answer:

$t=0, \pm \sqrt{3}$ (multiplicity of 1 on 0, multiplicity of 2 on $\pm \sqrt{3}$

Explanation:

First, pull out the common t and then factorize using quadratic factoring rules:

This equation has solutions at two values: when t=0 and when

$(t^2-3)^2=0\rightarrow t=\pm \sqrt{3}$ Therefore, But since the degree on the former equation is one and the degree on the latter equation is two, the multiplicities are 1 and 2 respectively.

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Example Question #1 : Find Complex Zeros Of A Polynomial Using The Fundamental Theorem Of Algebra

Find a fourth degree polynomial whose zeroes are -2, 5, and $-2\pm \sqrt{2i}$

Possible Answers:

x^4-16x^2-58x-60

x^3-16x^2-58x-60

x^4-x^3-16x^2-58x-60

x^4+x^3+16x^2+58x-60

x^4+x^3-16x^2-58x-60

Correct answer:

x^4+x^3-16x^2-58x-60

Explanation:

This one is a bit of a journey. The expressions for the first two zeroes are easily calculated, (x+2) and (x-5) respectively. The last expression must be broken up into two equations:

which are then set equal to zero to yield the expressions $(x+2-i\sqrt{2})$ and $(x+2+i\sqrt{2})$

Finally, we multiply together all of the parenthesized expressions, which multiplies out to x^4+x^3-16x^2-58x-60=0

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Example Question #1 : Find Complex Zeros Of A Polynomial Using The Fundamental Theorem Of Algebra

The third degree polynomial expression f(x)=x^3-x^2+4x-4 has a real zero at x=1 . Find all of the complex zeroes.

Possible Answers:

$x=\pm \sqrt{2}$

$x=\pm 2i$

$x=2\pm \sqrt{2i}$

$x=\pm 4i$

$x=2\pm 2i$

Correct answer:

$x=\pm 2i$

Explanation:

First, factor the expression by grouping:

$x^3-x^2+4x-4\rightarrow x^2(x-1)+4(x-1)\rightarrow (x^2+4)\cdot(x-1)$

To find the complex zeroes, set the term (x^2+4) equal to zero:

$x^2=-4\rightarrow x=\pm \sqrt{-2}=\pm 2i$

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Example Question #1 : Find Complex Zeros Of A Polynomial Using The Fundamental Theorem Of Algebra

Find all the real and complex zeros of the following equation: $2x^{5}+x^{4}-2x-1$

Possible Answers:

$x=1,-1,\frac{-1}{2},i$

$x=1,\frac{-1}{2},i$

$x=1, \frac{-1}{2},\pm i$

$x=1,\frac{-1}{2}$

$x=1, -1, \frac{-1}{2},\pm i$

Correct answer:

$x=1, -1, \frac{-1}{2},\pm i$

Explanation:

First, factorize the equation using grouping of common terms:

$2x^{5}+x^{4}-2x-1\rightarrow x^{4}(2x+1)-1(2x+1)\rightarrow (x^{4}-1)(2x+1)\rightarrow (x+1)(x-1)(x^{2}+1)(2x+1)$

Next, setting each expression in parentheses equal to zero yields the answers.

$(x+1)=0\rightarrow x=-1(x-1)=0\rightarrow x=1(x^{2}+1)=0\rightarrow x=\pm i{(2x+1)=0\rightarrow x=\frac{-1}{2}}$

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Example Question #1 : Find Complex Zeros Of A Polynomial Using The Fundamental Theorem Of Algebra

Find all the zeroes of the following equation and their multiplicity: $g(t)=t^{5}-6t^{3}+9t$

Possible Answers:

$t=0,\pm \sqrt{3}$ (multiplicity of 2 on 0, multiplicity of 1 on $\pm \sqrt{3}$ )

$t=0,\pm \sqrt{3}$ (multiplicity of 1 on 0, multiplicity of 2 on $\pm \sqrt{3}$ )

$t=0,\pm \sqrt{3i}$ (multiplicity of 2 on 0, multiplicity of 1 on $\pm \sqrt{3i}$ )

$t=0,\pm \sqrt{3i}$ (multiplicity of 1 on 0, multiplicity of 2 on $\pm \sqrt{3i}$ )

Correct answer:

$t=0,\pm \sqrt{3}$ (multiplicity of 1 on 0, multiplicity of 2 on $\pm \sqrt{3}$ )

Explanation:

First, pull out the common t and then factorize using quadratic factoring rules: $t^{5}-6t^{3}+9t\rightarrow t(t^{4}-6t^{2}+9)\rightarrow t(t^{2}-3)^{2}$

This equation has a solution as two values: when t=0 , and when $\left ( t^{2}-3 \right )^{2}=0\rightarrow t=\pm \sqrt{3}$ . Therefore, But since the degree on the former equation is one and the degree on the latter equation is two, the multiplicities are 1 and 2 respectively.

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Example Question #431 : Pre Calculus

Find a fourth-degree polynomial whose zeroes are -2,5 , and $-2\pm \sqrt{2i}$

Possible Answers:

$x^{4}+x^{3}+16x^{2}+58x-60$

$x^{4}-x^{3}-16x^{2}-58x-60$

$x^{3}-16x^{2}-58x-60$

$x^{4}-16x^{2}-58x-60$

$x^{4}+x^{3}-16x^{2}-58x-60$

Correct answer:

$x^{4}+x^{3}-16x^{2}-58x-60$

Explanation:

This one is a bit of a journey. The expressions for the first two zeroes are easily calculated, $\left ( x+2 \right )$ and $\left ( x-5 \right )$ respectively. The last expression must be broken up into two equations: $x=-2-i\sqrt{2},x=-2+i\sqrt{2}$ which are then set equal to zero to yield the expressions $\left ( x+2-i\sqrt{2} \right )$ and $\left ( x+2+i\sqrt{2} \right )$

Finally, we multiply together all of the parenthesized expressions, which multiplies out to $x^{4}+x^{3}-16x^{2}-58x-60=0$

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Example Question #432 : Pre Calculus

The third-degree polynomial expression $f(x)=x^{3}-x^{2}+4x-4$ has a real zero at x=1 . Find all of the complex zeroes.

Possible Answers:

Correct answer:

Explanation:

First, factor the expression by grouping: $x^{3}-x^{2}+4x-4\rightarrow x^{2}(x-1)+4(x-1)\rightarrow (x^{2}+4)\cdot (x-1)$

To find the complex zeroes, set the term $(x^{2}+4)$ equal to zero: $x^{2}=-4\rightarrow x=\pm \sqrt{-2}=\pm 2i$

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Example Question #1 : Find The Sum And Product Of The Zeros Of A Polynomial

Given y=5x^2+14x-3 , determine the sum and product of the zeros respectively.

Possible Answers:

$\frac{14}{5},-\frac{3}{5}$

$\frac{16}{5}, -\frac{3}{5}$

$-\frac{14}{5},-\frac{3}{5}$

$\frac{1}{5},-3$

$\frac{7}{5},-\frac{21}{5}$

Correct answer:

$-\frac{14}{5},-\frac{3}{5}$

Explanation:

To determine zeros of y=5x^2+14x-3 , factorize the polynomial.

5x^2+14x-3=(5x-1)(x+3)

Set each of the factorized components equal to zero and solve for .

5x-1=0

$x=\frac{1}{5}$

x+3=0

x=-3

The sum of the roots:

$\frac{1}{5}+(-3)= \frac{1}{5}-\frac{15}{5}= -\frac{14}{5}$

The product of the roots:

$(\frac{1}{5})(-3)= -\frac{3}{5}$

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Precalculus : Polynomial Functions

Study concepts, example questions & explanations for Precalculus

All Precalculus Resources

Example Questions

Example Question #1 : Find Complex Zeros Of A Polynomial Using The Fundamental Theorem Of Algebra

Example Question #1 : Find Complex Zeros Of A Polynomial Using The Fundamental Theorem Of Algebra

Example Question #1 : Find Complex Zeros Of A Polynomial Using The Fundamental Theorem Of Algebra

Example Question #1 : Find Complex Zeros Of A Polynomial Using The Fundamental Theorem Of Algebra

Example Question #1 : Find Complex Zeros Of A Polynomial Using The Fundamental Theorem Of Algebra

Example Question #1 : Find Complex Zeros Of A Polynomial Using The Fundamental Theorem Of Algebra

Example Question #1 : Find Complex Zeros Of A Polynomial Using The Fundamental Theorem Of Algebra

Example Question #431 : Pre Calculus

Example Question #432 : Pre Calculus

Example Question #1 : Find The Sum And Product Of The Zeros Of A Polynomial

All Precalculus Resources

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