TheXSquaredFactor

avatar
BenutzernameTheXSquaredFactor
Punkte2441
Membership
Stats
Fragen 3
Antworten 956

 #1
avatar+2441 
+3

Sure, I think I can give you a fairly simple proof for you. There are a few property of exponents that you have learned. I have listed all of them for you and what each says. To understand these proofs, you should understand that for whole numbers of a, \(x^a=\underbrace{x*x*x*...*x}\\ \quad\quad\quad\quad\text{a times}\). This is the basis of the notation. The proofs are based on the notation. Sometimes, some rules will assume that a previous one was already proven.

 

Property of Exponent Definition
1. Product of Powers \(x^{\textcolor{red}{a}}*x^{\textcolor{blue}{b}}=x^{\textcolor{red}{a}+\textcolor{blue}{b}}\)
2. Quotient of Powers \(\frac{x^{\textcolor{red}{a}}}{x^{\textcolor{blue}{b}}}=x^{\textcolor{red}{a}-\textcolor{blue}{b}}\)
3. Negative Exponents \(x^{\textcolor{blue}{-b}}=\frac{1}{x^\textcolor{blue}{b}}\\ \frac{1}{x^\textcolor{blue}{-b}}=x^{\textcolor{blue}{b}} \)
4. Power of a Power \(\left(x^{\textcolor{red}{a}}\right)^{\textcolor{blue}{b}}=x^{{\textcolor{red}{a}}\textcolor{blue}{b}}\)
5. Power of a Product \((xy)^\textcolor{red}{a}=x^\textcolor{red}{a}y^\textcolor{red}{a}\)
6. Power of a Quotient \(\left(\frac{x}{y}\right)^\textcolor{red}{a}=\frac{x^\textcolor{red}{a}}{y^\textcolor{red}{a}}\\ \left(\frac{x}{y}\right)^\textcolor{red}{-a}=\frac{y^\textcolor{red}{a}}{x^\textcolor{red}{a}}\)
   


I will write the proofs in order.

 

1) \(x^{\textcolor{red}{a}}*x^{\textcolor{blue}{b}}=\underbrace{\underbrace{x*x*x*...*x}*\underbrace{x*x*x..*x}\\ \hspace{7mm}\text{a times}\hspace{18mm}\text{b times}}\\ \hspace{40mm}\text{a+b times}\\ \), so \(x^{\textcolor{red}{a}}*x^{\textcolor{blue}{b}}=x^{{\textcolor{red}{a}}+{\textcolor{blue}{b}}}\)

 

 

2) \(\frac{x^{\textcolor{red}{a}}}{x^{\textcolor{blue}{b}}}=\frac{\underbrace{x*x*x*...*x}\\ \hspace{2mm}\text{a times}}{\underbrace{x*x*x*...*x}\\ \hspace{2mm}\text{b times}}\). Here, the x in the numerator will cancel out the x in the denominator a-b times, so \(\frac{x^{\textcolor{red}{a}}}{x^{\textcolor{blue}{b}}}=x^{\textcolor{red}{a}-\textcolor{blue}{b}}\)

 

3a) 

\(\frac{x^{\textcolor{red}{a}}}{x^{\textcolor{blue}{b}}}=x^{\textcolor{red}{a}-\textcolor{blue}{b}}\) This was established in the second proof. Set a=0 to get the case of x to the power of -b.
\(\frac{x^0}{x^{\textcolor{blue}{b}}}=x^{0{\textcolor{blue}{-b}}}\) x^0=1, except when x=0.
\(\frac{1}{x^{\textcolor{blue}{b}}}=x^{{\textcolor{blue}{-b}}}\)  
   

 

 

3b) 

\(\frac{1}{x^\textcolor{blue}{-b}}\) As we established in the previous proof, we can replace x^(-b) with 1/[x^(-b)]
\(\frac{1}{\frac{1}{x^\textcolor{blue}{b}}}*\frac{x^\textcolor{blue}{b}}{x^\textcolor{blue}{b}}\) Now, simplify this complex fraction. Notice how the denominators cancel out here.
\(x^\textcolor{blue}{b}\)  
   

 

 

4) \(\left(x^{\textcolor{red}{a}}\right)^{\textcolor{blue}{b}}=\underbrace{x^{\textcolor{red}{a}}*x^{\textcolor{red}{a}}*x^{\textcolor{red}{a}}*...*x^{\textcolor{red}{a}}}= x^{\underbrace{{\textcolor{red}{a}}+{\textcolor{red}{a}}+{\textcolor{red}{a}}+...+{\textcolor{red}{a}}}}\\ \hspace{27mm}\text{b times}\hspace{23mm}\text{b times}\) 

 

If there are b lots of a, this is equivalent to multiplication, so \(\left(x^{\textcolor{red}{a}}\right)^{\textcolor{blue}{b}}=x^{{\textcolor{red}{a}}\textcolor{blue}{b}}\)

 

5) \((xy)^\textcolor{red}{a}=\underbrace{xy*xy*xy*...*xy}=\underbrace{(x*x*x*...*x)}*\underbrace{(y*y*y...*y)}=x^\textcolor{red}{a}y^\textcolor{red}{a}\\ \hspace{27mm}\text{a times}\hspace{27mm}\text{a times}\hspace{22mm}\text{a times}\)

 

If we multiply lots of x and y a times, then we can convert this back to an exponent.

 

6a) \(\left(\frac{x}{y}\right)^\textcolor{red}{a}=\underbrace{\frac{x}{y}*\frac{x}{y}*\frac{x}{y}*...*\frac{x}{y}} =\underbrace{(x*x*x*...*x)}*\underbrace{\left(\frac{1}{y}*\frac{1}{y}*\frac{1}{y}*...*\frac{1}{y}\right)} =\frac{x^\textcolor{red}{a}}{1}*\frac{1}{y^\textcolor{red}{a}}=\frac{x^\textcolor{red}{a}}{y^\textcolor{red}{a}}\\ \hspace{27mm}\text{a times}\hspace{22mm}\text{a times}\hspace{25mm}\text{a times}\)

 

6b) 

\(\left(\frac{x}{y}\right)^\textcolor{red}{-a}\) Use the negative exponents rule that we already proved.
\(\frac{1}{\left(\frac{x}{y}\right)^\textcolor{red}{a}}\) Use the rule we used in 6a.
\(\frac{1}{\frac{x^\textcolor{red}{a}}{y^\textcolor{red}{a}}}*\frac{\frac{y^\textcolor{red}{a}}{x^\textcolor{red}{a}}}{\frac{y^\textcolor{red}{a}}{x^\textcolor{red}{a}}}\) Of course, we are only multiplying the fraction by one, which does not actually change the value at all. Now, a lot of canceling occurs in the denominator.
\(\frac{y^\textcolor{red}{a}}{x^\textcolor{red}{a}}\)  
   

 

 Hopefully, these proofs will aide you in your math journey. Always question why something is and don't accept them as fact!

 #1
avatar+2441 
+2

\(f(x)=ax^2+bx+a\) 

 

If one root is located at x=4, then we can find an equation for this.

 

\(f(x)=ax^2+bx+a\) Substitute in \(f(x)=0\) and \(x=4\) and simplify completely.
\(0=a(4)^2+b*4+a\)  
\(0=16a+4b+a\) On the right hand side, the 16a and a are like terms, so they will combine.
\(0=17a+4b\) Let's solve for b now by subtracting 17a from both sides.
\(-17a=4b\) Divide by 4 to completely isolate b.
\(-\frac{17a}{4}=b\)  
   

 

Since we now know what equals in terms of a, we can simplify the original function to \(f(x)=ax^2-\frac{17a}{4}x+a\). We can now begin to solve this and find the other root.

 

\(f(x)=ax^2-\frac{17a}{4}x+a\) First off, factor out the GCF from the right hand side. In this case, the GCF will be a. Let's actually divide by a and get rid of it. The problem states that a is both a nonzero constant, so this is a valid operation. Of course, we only care about the zeros of this particular function, so let's set f(x) equal to 0.
\(0=x^2-\frac{17}{4}x+1\) It may be to difficult to work with fractions, so it will be beneficial to rid the problem of any and all fractions. Eliminating the fraction can be accomplished by mutliplying both sides by 4.
\(0=4x^2-17x+4\) Break up the b-term, -17, into parts that can be factored.
\(0=(4x^2-16x)+(-x+4)\) Complete factoring by grouping. This requires finding the GCF of both groups (indicated by the parentheses).
\(0=4x(x-4)-1(x-4)\) 4x and -1 are being multiplied by the same quantity, so we can combine this into a factored form.
\(0=(4x-1)(x-4)\) Set each factor equal to zero and solve.
\(4x-1=0\) \(x-4=0\)

 

 
\(4x=1\) \(x=4\)

 

 
\(x_1=\frac{1}{4}\) \(x_2=4\)

 

It should be reassuring that we found that x=4 is a zero of this polynomial function because that information was given in the problem.
   

 

Therefore, x=1/4 is the other zero of this polynomial function.

 #2
avatar+2441 
+1

Let's break this equation down step-by-step. Let's start with the solid line that goes upward from left to right first. The most useful type of linear equation is slope-intercept because it is easy to build the equation based on individual features of each linear equation.Let's pretend, for now, that the lines are not inequalities and instead equations.

 

\(y=mx+b\) Visually, the y-intercept is at (0,1), which allows us to plug y-coordinate of this corordinate in for b.
\(y=mx+1\) The slope can be calculated by observing rise over run here. In this case, the difference in the y-coordinates divided by the difference in the x-coordinates equals 2/7.
\(y=\frac{2}{7}x+1\) There are two problems with the equation we have generated thus far. One is that it is not an inequality. Secondly, it looks nothing like the given equations in the answer choices. First, let's deal with the correct inequality sign. Since the shaded region contains all the y-values below the original output, we know that we need a less-than-or-equal-to sign.
\(y\leq\frac{2}{7}x+1\) Now, we need to convert this into standard form so that we can compare this answer with the others provided. Eliminate the fraction since none of the answer choices contain a fraction anywhere.
\(7y\leq 2x+7\) Let's subtract 7 from both sides.
\(7y-7\leq 2x\)  
   

 

This immediately eliminates the last option since the inequality symbol is inverted, which in incorrect. Unfortunately, though, we can manipulate this answer and get the rest of the answers, so we will have to move on to the next line. Let's do the solid line that goes downward from left to right. Let's utilize the exact same process as before. 

 

\(y=mx+b\) The y-intercept appears to be located at the Cartesian coordinate (0,-8) and the slope is -2.
\(y=-2x-8\) Now, let's consider the inequality symbol. Every value on the line and less than what the line produced is shaded, so there needs to be a less-than-or-equal-to symbol for a second time instead of an equal sign.
\(y\leq -2x-8\) Multiply by 2 on both sides to eliminate the fraction, as it is difficult to compare the answer choices with the fraction remaining.
   

 

We can eliminate the first answer choice once again because the sign is incorrect. We can also eliminate the second option choice, too, because it is incorrect as well. It is 

 

\(-y\leq 2x+8\)

 

This is invalid because when multiplying or dividing by a negative number, the inequality sign is flipped, so this is incorrect, too. 

 

Therefore, there is no need to check for the other line, so the third option is correct.