HiSET: Math : Identification

Study concepts, example questions & explanations for HiSET: Math

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Example Questions

Example Question #1 : Identification

The equation

\(\displaystyle x^{2} + 34 = 17x\)

has two distinct solutions. What is their sum?

Possible Answers:

\(\displaystyle -17\)

\(\displaystyle -34\)

\(\displaystyle 17\)

\(\displaystyle 34\)

\(\displaystyle 0\)

Correct answer:

\(\displaystyle -17\)

Explanation:

It is not necessary to actually find the solutions to a quadratic equation to determine the sum of its solutions.

First, get the equation in standard form \(\displaystyle ax^{2}+ bx + c = 0\) by subtracting \(\displaystyle 17x\) from both sides:

\(\displaystyle x^{2} + 34 = 17x\)

\(\displaystyle x^{2} + 34 -17x = 17x - 17x\)

\(\displaystyle x^{2} -17x + 34 = 0\)

If a quadratic equation has two distinct solutions, which we are given here, their sum is the linear coefficient \(\displaystyle b\). In this problem, \(\displaystyle b= -17\), making \(\displaystyle -17\) the correct choice.

Example Question #44 : Algebraic Concepts

The graph of the polynomial function

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

has one and only one zero on the interval \(\displaystyle (0, 1)\). On which subinterval is it located?

Possible Answers:

\(\displaystyle (0.8, 1)\)

\(\displaystyle (0.2, 0.4)\)

\(\displaystyle (0.4, 0.6)\)

\(\displaystyle (0, 0.2)\)

\(\displaystyle (0,6, 0.8)\)

Correct answer:

\(\displaystyle (0.4, 0.6)\)

Explanation:

The Intermediate Value Theorem (IVT) states that if the graph of a function \(\displaystyle f\) is continuous on an interval \(\displaystyle [a, b]\), and \(\displaystyle f(a)\) and \(\displaystyle f(b)\) differ in sign, then \(\displaystyle f\) has a zero on \(\displaystyle (a,b)\). Consequently, the way to answer this question is to determine the signs of \(\displaystyle f\) on the endpoints of the subintervals - \(\displaystyle \left \{ 0, 0.2, 0.4, 0.6, 0.8, 1 \right \}\). We can do this by substituting each value for \(\displaystyle x\) as follows:

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

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

\(\displaystyle f(0.2)= 0.2^{3}+0.2^{2}-5(0.2)+2 = 0.008+0.04-1+2 = 1.048\)

\(\displaystyle f(0.4)= 0.4^{3}+0.4^{2}-5(0.4)+2= 0.064+ 0.16- 2+2 = 0.224\)

\(\displaystyle f(0.6)= 0.6^{3}+0.6^{2}-5(0.6)+2= 0.216+ 0.36- 3+2 = -0.424\)

\(\displaystyle f(0.8)= 0.8^{3}+0.8^{2}-5(0.8)+2= 0.512+ 0.64- 4+2 = -0.848\)

\(\displaystyle f(1)=1^{3}+1^{2}-5(1)+2 =1+1-5+2=-1\)

\(\displaystyle f\) assumes positive values for \(\displaystyle x= 0, 0.2, 0.4\) and negative values for \(\displaystyle x = 0.6, 0.8, 1\). By the IVT, \(\displaystyle f\) has a zero on \(\displaystyle (0.4, 0.6)\).

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