SAT II Math I : Graphing Functions

Study concepts, example questions & explanations for SAT II Math I

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Example Questions

Example Question #10 : Graphing Quadratic Functions

How many points of intersection could two distinct quadratic functions have?

\(\displaystyle I\)\(\displaystyle 0\)

\(\displaystyle II\).  \(\displaystyle 1\)

\(\displaystyle III\)\(\displaystyle 2\)

 

Possible Answers:

\(\displaystyle I\) only

\(\displaystyle II\) only

\(\displaystyle I\) and \(\displaystyle II\)

\(\displaystyle II\) and \(\displaystyle III\)

\(\displaystyle I\)\(\displaystyle II\), and \(\displaystyle III\)

Correct answer:

\(\displaystyle I\)\(\displaystyle II\), and \(\displaystyle III\)

Explanation:

An intersection of two functions is a point they share in common. A diagram can show all the possible solutions:

Quadratics

Notice that:

\(\displaystyle f(x)\) and \(\displaystyle h(x)\) intersect \(\displaystyle 0\) times

\(\displaystyle f(x)\) and \(\displaystyle g(x)\) intersect \(\displaystyle 1\) time

\(\displaystyle g(x)\) and \(\displaystyle h(x)\) intersect \(\displaystyle 2\) times

The diagram shows that \(\displaystyle I\), \(\displaystyle II\), and \(\displaystyle III\) are all possible. 

 

Example Question #21 : Graphing Functions

Which of the following graphs matches the function \(\displaystyle y=(x-1)^2-2\)?

Possible Answers:

Graph2

Graph1

Graph3

Graph4

Graph

Correct answer:

Graph

Explanation:

Start by visualizing the graph associated with the function \(\displaystyle y=x^2\):

Graph5

Terms within the parentheses associated with the squared x-variable will shift the parabola horizontally, while terms outside of the parentheses will shift the parabola vertically. In the provided equation, 2 is located outside of the parentheses and is subtracted from the terms located within the parentheses; therefore, the parabola in the graph will shift down by 2 units. A simplified graph of \(\displaystyle y=x^2-2\) looks like this:

Graph6

Remember that there is also a term within the parentheses. Within the parentheses, 1 is subtracted from the x-variable; thus, the parabola in the graph will shift to the right by 1 unit. As a result, the following graph matches the given function \(\displaystyle y=(x-1)^2-2\) :

Graph

Example Question #21 : Graphing Functions

Simplify the following expression:

\(\displaystyle \mid -3x\mid +5-2x-\mid -5\mid\)

Possible Answers:

\(\displaystyle -5x+10\)

\(\displaystyle x+10\)

\(\displaystyle -5x\)

\(\displaystyle x\)

Correct answer:

\(\displaystyle x\)

Explanation:

\(\displaystyle \mid -3x\mid +5-2x-\mid -5\mid\)

To simplify, we must first simplify the absolute values.

\(\displaystyle 3x+5-2x-5\)

Now, combine like terms:

\(\displaystyle x\)

Example Question #22 : Graphing Functions

\(\displaystyle f(x)=5x^{5}-3x^{2}+7\)

Where does \(\displaystyle f(x)\) cross the \(\displaystyle y\) axis?

Possible Answers:

-7

7

-3

5

3

Correct answer:

7

Explanation:

\(\displaystyle f(x)\) crosses the \(\displaystyle y\) axis when \(\displaystyle x\) equals 0. So, substitute in 0 for \(\displaystyle x\):

\(\displaystyle f(x)=5x^{5}-3x^{2}+7\)

\(\displaystyle f(0)=5(0)^{5}-3(0)^{2}+7\)

\(\displaystyle f(0)=7\)

Example Question #142 : Functions And Graphs

Screen_shot_2014-12-24_at_2.27.32_pm

Which of the following is an equation for the above parabola?

Possible Answers:

\(\displaystyle y=(x-2)(x+3)\)

\(\displaystyle y=\frac{1}{2}(x+3)(x-2)\)

\(\displaystyle y=\frac{1}{2}(x-3)(x+2)\)

\(\displaystyle y=(x-3)(x+2)\)

Correct answer:

\(\displaystyle y=\frac{1}{2}(x-3)(x+2)\)

Explanation:

The zeros of the parabola are at \(\displaystyle 3\) and \(\displaystyle -2\), so when placed into the formula 

\(\displaystyle y=C(x-z_{1})(x-z_{2})\)

each of their signs is reversed to end up with the correct sign in the answer. The coefficient can be found by plugging in any easily-identifiable, non-zero point to the above formula. For example, we can plug in \(\displaystyle (4,3)\) which gives 

\(\displaystyle 3=C(4-3)(4+2)\)  

\(\displaystyle 6C=3\)

\(\displaystyle C=\frac{1}{2}\)

Example Question #141 : Functions And Graphs

Which equation best represents the following graph?

Graph6

Possible Answers:

\(\displaystyle y(x)=-(x+1)^2-1\)

\(\displaystyle y(x)=-(x+1)^3-1\)

\(\displaystyle y(x)=e^{2x-1}+\frac{1}{9}\)

None of these

\(\displaystyle y(x)=-x-1\)

Correct answer:

\(\displaystyle y(x)=-(x+1)^3-1\)

Explanation:

We have the following answer choices.

  1. \(\displaystyle y(x)=-(x + 1)^3 - 1\)
  2. \(\displaystyle y(x)=-(x + 1)^2 - 1\)
  3. \(\displaystyle y(x)=-x - 1\)
  4. \(\displaystyle y(x)=e^{2x-1}+\frac{1}{9}\)

The first equation is a cubic function, which produces a function similar to the graph. The second equation is quadratic and thus, a parabola. The graph does not look like a prabola, so the 2nd equation will be incorrect. The third equation describes a line, but the graph is not linear; the third equation is incorrect. The fourth equation is incorrect because it is an exponential, and the graph is not an exponential. So that leaves the first equation as the best possible choice.

Example Question #1 : Graphing Polynomial Functions

Which of the graphs best represents the following function?

\(\displaystyle f(x)=\frac{9}{10}x^2-7x+2\)

Possible Answers:

None of these

Graph_cube_

Graph_exponential_

Graph_parabola_

Graph_line_

Correct answer:

Graph_parabola_

Explanation:

\(\displaystyle f(x)=\frac{9}{10}x^2-7x+2\)

The highest exponent of the variable term is two (\(\displaystyle x^2\)). This tells that this function is quadratic, meaning that it is a parabola.

The graph below will be the answer, as it shows a parabolic curve.

Graph_parabola_

Example Question #1 : Graphing Polynomial Functions

Which of the following is a graph for the following equation:

\(\displaystyle x^8+x^7-x^4+10\)

Possible Answers:

Cannot be determined

Incorrect 1

Incorrect 3

Correct answer

Incorrect 2

Correct answer:

Correct answer

Explanation:

The way to figure out this problem is by understanding behavior of polynomials.

The sign that occurs before the \(\displaystyle x^8\) is positive and therefore it is understood that the function will open upwards. the "8" on the function is an even number which means that the function is going to be u-shaped. The only answer choice that fits both these criteria is:

 Correct answer

Example Question #22 : Graphing Functions

Define a function \(\displaystyle f(x) = x^{5}+ 4x^{2}\).

\(\displaystyle f(c) = 7\) for exactly one real value of \(\displaystyle c\) on the interval \(\displaystyle (1,0. 1.5)\).

Which of the following statements is correct about \(\displaystyle c\)?

Possible Answers:

\(\displaystyle c \in (1.0, 1.1 )\)

\(\displaystyle c \in ( 1.2, 1.3)\)

\(\displaystyle c \in ( 1.3, 1.5)\)

\(\displaystyle c \in (1.1, 1.2)\)

\(\displaystyle c \in ( 1.3, 1.4)\)

Correct answer:

\(\displaystyle c \in (1.1, 1.2)\)

Explanation:

Define \(\displaystyle g(x)= f(x) - 7 = x^{5}+ 4x^{2} -7\). Then, if \(\displaystyle g(c)= f(c) - 7 = 0\), it follows that \(\displaystyle f(c) = 7\).

By the Intermediate Value Theorem (IVT), if \(\displaystyle g(x)\) is a continuous function, and \(\displaystyle g(a)\) and \(\displaystyle g(b)\) are of unlike sign, then \(\displaystyle g(c) = 0\) for some \(\displaystyle c \in (a, b)\). As a polynomial, \(\displaystyle g(x)\) is a continuous function, so the IVT applies here.

Evaluate \(\displaystyle g(x)\) for each of the following values: \(\displaystyle \left \{ 1.0, 1.1, 1.2, 1.3, 1.4, 1.5\right \}\)

\(\displaystyle g(1.0) = 1.0^{5}+ 4 \cdot 1.0^{2} -7 = -2\)

\(\displaystyle g(1.1) = 1.1^{5}+ 4 \cdot 1.1^{2} -7 \approx -0.55\)

\(\displaystyle g(1.2) = 1.2^{5}+ 4 \cdot 1.2^{2} -7 \approx 1.24\)

\(\displaystyle g(1.3) = 1.3^{5}+ 4 \cdot 1.3^{2} -7 \approx 3.47\)

\(\displaystyle g(1.4) = 1.4^{5}+ 4 \cdot 1.4^{2} -7 \approx 6.22\)

\(\displaystyle g(1.5) = 1.5^{5}+ 4 \cdot 1.5^{2} -7 \approx 9.59\)

Only in the case of \(\displaystyle (1.1, 1.2)\) does it hold that \(\displaystyle g (x)\) assumes a different sign at both endpoints - \(\displaystyle g(1.1) < 0 < g(1.2)\). By the IVT, \(\displaystyle g(c) = 0\), and \(\displaystyle f(c) = 7\), for some \(\displaystyle c \in (1.1, 1.2)\).

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