Chapter 2: Problem 6
Solve each equation. $$|5-6 x|=0$$
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Chapter 2: Problem 6
Solve each equation. $$|5-6 x|=0$$
These are the key concepts you need to understand to accurately answer the question.
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In this exercise we investigate the effect of the constant \(c\) upon the roots of the quadratic equation \(x^{2}-6 x+c=0\) We do this by looking at the \(x\) -intercepts of the graphs of the corresponding equations \(y=x^{2}-6 x+c\) (a) Set a viewing rectangle that extends from 0 to 5 in the \(x\) -direction and from -2 to 3 in the \(y\) -direction. Then (on the same set of axes) graph the equations \(y=x^{2}-6 x+c\) with \(c\) running from 8 to 10 at increments of \(0.25 .\) In other words, graph the equations \(y=x^{2}-6 x+8, y=x^{2}-6 x+8.25, y=x^{2}-6 x+8.50\) and so on, up through \(y=x^{2}-6 x+10\) (b) Note from the graphs in part (a) that, initially, as \(c\) increases, the \(x\) -intercepts draw closer and closer together. For which value of \(c\) do the two \(x\) -intercepts seem to merge into one? (c) Use algebra as follows to check your observation in part (b). Using that value of \(c\) for which there appears to be only one intercept, solve the quadratic equation \(x^{2}-6 x+c=0 .\) How many roots do you obtain? (d) Some of the graphs in part (a) have no \(x\) -intercepts. What are the corresponding values of \(c\) in these cases? Pick any one of these values of \(c\) and use the quadratic formula to solve the equation \(x^{2}-6 x+c=0 .\) What happens?
Solve the inequalities Suggestion: A calculator may be useful for approximating key numbers. $$\left(x-\frac{1}{2}\right)\left(x+\frac{1}{2}\right)\left(x+\frac{3}{2}\right)<0$$
Solve the inequalities. Suggestion: A calculator may be useful for approximating key numbers. $$\frac{1}{x-2}-\frac{1}{x-1} \geq \frac{1}{6}$$
Let \(a, b,\) and \(c\) be nonnegative numbers. Follow steps (a) through (e) to show that $$\sqrt[3]{a b c} \leq \frac{a+b+c}{3}$$ with equality holding if and only if \(a=b=c\). This result is known as the arithmetic-geometric mean inequality for three numbers. (Applications are developed in the projects at the ends of Sections 4.6 and \(4.7 .\) ) (a) By multiplying out the right-hand side, show that the following equation holds for all real numbers \(A, B\) and \(C\) $$\begin{aligned} 3 A B C=& A^{3}+B^{3}+C^{3}-\frac{1}{2}(A+B+C) \\ & \times\left[(A-B)^{2}+(B-C)^{2}+(C-A)^{2}\right] \quad \quad (1) \end{aligned}$$ (b) Now assume for the remainder of this exercise that \(A\) \(B,\) and \(C\) are nonnegative numbers. Use equation (1) to explain why $$3 A B C \leq A^{3}+B^{3}+C^{3}\quad \quad (2)$$ (c) Make the following substitutions in inequality ( 2 ): \(A^{3}=a, B^{3}=b,\) and \(C^{3}=c .\) Show that the result can be written $$\sqrt[3]{a b c} \leq \frac{a+b+c}{3} \quad \quad (3)$$ (d) Assuming that \(a=b=c,\) show that inequality (3) becomes an equality. (e) Assuming \(\sqrt[3]{a b c}=\frac{a+b+c}{3},\) show that \(a=b=c\) Hint: In terms of \(A, B,\) and \(C,\) the assumption becomes \(A B C=\frac{A^{3}+B^{3}+C^{3}}{3} .\) Use this to substitute for \(A B C\) on the left-hand side of equation (1). Then use the resulting equation to deduce that \(A=B=C,\) and consequently \(a=b=c\)
Solve the inequalities. Suggestion: A calculator may be useful for approximating key numbers. $$\frac{x^{2}-x-1}{x^{2}+x-1}>0$$
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