Algebra II : Introduction to Functions

Study concepts, example questions & explanations for Algebra II

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Example Questions

Example Question #171 : Introduction To Functions

Determine the value of \(\displaystyle \frac{a}{c}-\frac{b}{d}\) if:  \(\displaystyle a=1, b=2,c=3, d=5\).

Possible Answers:

\(\displaystyle -\frac{11}{15}\)

\(\displaystyle -\frac{1}{15}\)

\(\displaystyle -\frac{6}{5}\)

\(\displaystyle \frac{1}{15}\)

\(\displaystyle -\frac{11}{6}\)

Correct answer:

\(\displaystyle -\frac{1}{15}\)

Explanation:

Substitute the values of \(\displaystyle a=1, b=2,c=3, d=5\) into the expression.

\(\displaystyle \frac{a}{c}-\frac{b}{d} = \frac{1}{3}-\frac{2}{5}\)

In order to subtract these fractions, we will need a least common denominator.

Multiply the denominators together for the LCD.  Convert the two fractions.

\(\displaystyle \frac{1}{3}-\frac{2}{5} = \frac{1(5)}{3(5)}-\frac{2(3)}{5(3)} = \frac{5}{15}-\frac{6}{15}\)

Subtract the numerators now that the denominators are common.

The answer is:  \(\displaystyle -\frac{1}{15}\)

Example Question #171 : Introduction To Functions

Determine the value of \(\displaystyle a^3-b^2-c\) if:  \(\displaystyle a=-1, b=-3, c=-5\)

Possible Answers:

\(\displaystyle 7\)

\(\displaystyle -5\)

\(\displaystyle 9\)

\(\displaystyle 13\)

\(\displaystyle 5\)

Correct answer:

\(\displaystyle -5\)

Explanation:

Given the expression \(\displaystyle a^3-b^2-c\) and the assigned values, substitute the values into the expression.

\(\displaystyle (-1)^3-(-3)^2-(-5)\)

Simplify this expression by order of operations.

\(\displaystyle -1-(9)+5 = -10+5 = -5\)

The answer is:   \(\displaystyle -5\)

Example Question #41 : Function Notation

Evaluate \(\displaystyle a^2-b^3\) if \(\displaystyle a=-6\) and \(\displaystyle b =-3\)

Possible Answers:

\(\displaystyle 3\)

\(\displaystyle 73\)

\(\displaystyle 21\)

\(\displaystyle 63\)

\(\displaystyle 9\)

Correct answer:

\(\displaystyle 63\)

Explanation:

Substitute the known values into the expression.

\(\displaystyle a^2-b^3 = (-6)^2-(-3)^3\)

Simplify the expression.

\(\displaystyle 36-(-27) = 36+27 = 63\)

The answer is:  \(\displaystyle 63\)

Example Question #41 : Function Notation

If \(\displaystyle a=-1\) and \(\displaystyle b= -2\), what is \(\displaystyle a^b\times b^a\)

Possible Answers:

\(\displaystyle -8\)

\(\displaystyle -\frac{1}{2}\)

\(\displaystyle -\frac{1}{4}\)

\(\displaystyle -2\)

\(\displaystyle 2\)

Correct answer:

\(\displaystyle -\frac{1}{2}\)

Explanation:

Substitute the assigned values into the expression.

\(\displaystyle (-1)^{(-2)}\times (-2)^{(-1)}\)

Simplify the negative exponents by rewriting both terms as fractions.

\(\displaystyle x^{-a} =\frac{1}{x^a}\)

\(\displaystyle (-1)^{(-2)}\times (-2)^{(-1)}= \frac{1}{(-1)^2} \times \frac{1}{(-2)^{1}}\)

Simplify the fractions.

\(\displaystyle 1\times \frac{1}{-2} = -\frac{1}{2}\)

The answer is:  \(\displaystyle -\frac{1}{2}\)

Example Question #173 : Functions And Graphs

If \(\displaystyle f(2)=5\), what must \(\displaystyle A\) be?  \(\displaystyle y = 3x(A-7)\)

Possible Answers:

\(\displaystyle \frac{56}{3}\)

\(\displaystyle \frac{107}{15}\)

\(\displaystyle \frac{81}{4}\)

\(\displaystyle \frac{97}{6}\)

\(\displaystyle \frac{47}{6}\)

Correct answer:

\(\displaystyle \frac{47}{6}\)

Explanation:

Substitute the known value of \(\displaystyle x=2, y=5\) into the equation.

\(\displaystyle 5= 3[2](A-7)\)

Simplify the equation.

\(\displaystyle 5=6(A-7)\)

Solve the right side by distribution.

\(\displaystyle 5=6A-42\)

Add 42 on both sides.

\(\displaystyle 5+42=6A-42+42\)

\(\displaystyle 47=6A\)

Divide by six on both sides.

\(\displaystyle \frac{47}{6}=\frac{6A}{6}\)

The answer is:  \(\displaystyle \frac{47}{6}\)

Example Question #47 : Function Notation

If \(\displaystyle f(2) = 4\), what must \(\displaystyle k\) equal in \(\displaystyle f(x) = 5x-k\)?

Possible Answers:

\(\displaystyle 18\)

\(\displaystyle 6\)

\(\displaystyle -18\)

\(\displaystyle -14\)

\(\displaystyle -8\)

Correct answer:

\(\displaystyle 6\)

Explanation:

The term \(\displaystyle f(2) = 4\) means that \(\displaystyle f(x)=4\) when \(\displaystyle x=2\).

Substitute the terms in the function to solve for \(\displaystyle k\).

\(\displaystyle 4 = 5(2)-k\)

Solve for \(\displaystyle k\).

\(\displaystyle 4 = 10-k\)

Subtract 10 on both sides.

\(\displaystyle 4 -10= 10-k-10\)

\(\displaystyle -6 =-k\)

Divide by negative one to eliminate the negative signs.

\(\displaystyle \frac{-6 }{-1}=\frac{-k}{-1}\)

The answer is:  \(\displaystyle 6\)

Example Question #41 : Function Notation

Which of the following is the equation of a vertical asymptote of the graph of the function \(\displaystyle f(x) = \frac{x+7}{x^{2}- 16}\) ?

(a) \(\displaystyle x= -7\)

(b) \(\displaystyle x= -4\)

(c) \(\displaystyle x= 4\)

Possible Answers:

(b) and (c) only 

(a) only

(c) only

(b) only

All three of (a), (b), and (c)

Correct answer:

(b) and (c) only 

Explanation:

The vertical asymptote(s) of the graph of a rational function such as \(\displaystyle f(x)\) can be found by evaluating the zeroes of the denominator after the rational expression is reduced. The expression is in simplest form, so set the denominator equal to 0 and solve for \(\displaystyle x\):

\(\displaystyle x^{2} - 16 = 0\)

Add 16 to both sides:

\(\displaystyle x^{2} - 16 + 16 = 0+ 16\)

\(\displaystyle x^{2} =16\)

Take the positive and negative square roots:

\(\displaystyle x = -\sqrt{16 } = -4\)

or 

\(\displaystyle x = \sqrt{16 } = 4\)

The graph of \(\displaystyle f(x)\) has two vertical asymptotes, the graphs of the lines \(\displaystyle x = -4\) and \(\displaystyle x= 4\).

Example Question #41 : Function Notation

If \(\displaystyle g(x)=5x+6x^2+3\) and \(\displaystyle f(x)=x-4\) what is \(\displaystyle g(f(x))\)?

Possible Answers:

\(\displaystyle 6x^2+5x-1\)

\(\displaystyle 6x^2-53x+119\)

\(\displaystyle 6x^2-43x+79\)

\(\displaystyle 6x^2+5x+79\)

Correct answer:

\(\displaystyle 6x^2-43x+79\)

Explanation:

\(\displaystyle g(f(x))\) is a composite function which means that the inside function is plugged into the outside function. So in this case, \(\displaystyle f(x)\) is plugged into \(\displaystyle g(x)\). In other words, replace the \(\displaystyle f(x)\) expression each time there is an \(\displaystyle x\) in the \(\displaystyle g(x)\) expression. 

 

In this case \(\displaystyle x-4\) would be plugged into each \(\displaystyle x\) in the \(\displaystyle g(x)\) expression. See below:

 

\(\displaystyle 5(x-4)+6(x-4)^2+3\)

 

This is then simplified to:

 

\(\displaystyle 5x-20+6x^2-48x+96+3\)

 

And then further simplified to:

 

\(\displaystyle 6x^2-43x+79\)

Example Question #1 : Transformations

\(\displaystyle f(x)=x^{2}\)

\(\displaystyle g(x)=4x^{2}-3\)

How is the graph of \(\displaystyle g(x)\) different from the graph of \(\displaystyle f(x)\)?

Possible Answers:

\(\displaystyle g(x)\) is wider than \(\displaystyle f(x)\) and is shifted down 3 units

\(\displaystyle g(x)\) is narrower than \(\displaystyle f(x)\) and is shifted down 3 units

\(\displaystyle g(x)\) is narrower than \(\displaystyle f(x)\) and is shifted up 3 units

\(\displaystyle g(x)\) is wider than \(\displaystyle f(x)\) and is shifted to the right 3 units

\(\displaystyle g(x)\) is narrower than \(\displaystyle f(x)\) and is shifted to the left 3 units

Correct answer:

\(\displaystyle g(x)\) is narrower than \(\displaystyle f(x)\) and is shifted down 3 units

Explanation:

Almost all transformed functions can be written like this:

\(\displaystyle g(x)=a[f(b(x-c))]+d\)

where \(\displaystyle f(x)\) is the parent function. In this case, our parent function is \(\displaystyle f(x)=x^{2}\), so we can write \(\displaystyle g(x)\) this way:

\(\displaystyle g(x)=a[b(x-c)]^{2}+d\)

Luckily, for this problem, we only have to worry about \(\displaystyle a\) and \(\displaystyle d\).

\(\displaystyle a\) represents the vertical stretch factor of the graph.

  • If \(\displaystyle |a|\) is less than 1, the graph has been vertically compressed by a factor of \(\displaystyle |a|\). It's almost as if someone squished the graph while their hands were on the top and bottom. This would make a parabola, for example, look wider.
  • If \(\displaystyle |a|\) is greater than 1, the graph has been vertically stretched by a factor of \(\displaystyle |a|\). It's almost as if someone pulled on the graph while their hands were grasping the top and bottom. This would make a parabola, for example, look narrower.

\(\displaystyle d\) represents the vertical translation of the graph.

  • If \(\displaystyle d\) is positive, the graph has been shifted up \(\displaystyle d\) units.
  • If \(\displaystyle d\) is negative, the graph has been shifted down \(\displaystyle d\) units.

 

For this problem, \(\displaystyle a\) is 4 and \(\displaystyle d\) is -3, causing vertical stretch by a factor of 4 and a vertical translation down 3 units.

Example Question #2 : Transformations

Which of the following transformations represents a parabola shifted to the right by 4 and halved in width?

Possible Answers:

\(\displaystyle f(x) = 2x^2 - 4\)

\(\displaystyle f(x)=2x^2+4\)

\(\displaystyle f(x) = 2(x+4)^2\)

\(\displaystyle f(x) = 0.5(x-4)^2\)

\(\displaystyle f(x) = 2(x-4)^2\)

Correct answer:

\(\displaystyle f(x) = 2(x-4)^2\)

Explanation:

Begin with the standard equation for a parabola: \(\displaystyle f(x)=x^2\).

Horizontal shifts are represented by additions (leftward shifts) or subtractions (rightward shifts) within the parenthesis of the \(\displaystyle x\) term. To shift 4 units to the right, subtract 4 within the parenthesis.

\(\displaystyle f(x)=(x-4)^2\)

The width of the parabola is determined by the magnitude of the coefficient in front of \(\displaystyle x\). To make a parabola narrower, use a whole number coefficient. Halving the width indicates a coefficient of two.

\(\displaystyle f(x) = 2(x-4)^2\)

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