Chapter 7: Problem 44
What does it mean if two quantities vary directly?
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Chapter 7: Problem 44
What does it mean if two quantities vary directly?
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Add or subtract as indicated. Simplify the result, if possible. $$\frac{4 x+3}{x^{2}-9}-\frac{x+1}{x-3}$$
Two formulas that approximate the dosage of a drug prescribed for children are $$ \begin{aligned} \text { Young's rule: } & C=\frac{D A}{A+12} \\ \text { and Cowling's rule: } & C=\frac{D(A+1)}{24} \end{aligned} $$ In each formula, \(A=\) the child's age, in years, \(D=\) an adult dosage, and \(C=\) the proper child's dosage. The formulas apply for ages 2 through \(13,\) inclusive. Use the formulas to solve Exercises \(93-96\) Use Young's rule to find the difference in a child's dosage for an 8 -year-old child and a 3 -year-old child. Express the answer as a single rational expression in terms of \(D .\) Then describe what your answer means in terms of the variables in the model.
Add or subtract as indicated. Simplify the result, if possible. $$\frac{7}{5 y^{2}-5 y}-\frac{2}{5 y-5}$$
Add or subtract as indicated. Simplify the result, if possible. $$\frac{y}{y^{2}-1}+\frac{2 y}{y-y^{2}}$$
Exercises \(123-125\) will help you prepare for the material covered in the next section. a. Add: \(\frac{1}{3}+\frac{2}{5}\) b. Subtract: \(\frac{2}{5}-\frac{1}{3}\) c. Use your answers from parts (a) and (b) to find \(\left(\frac{1}{3}+\frac{2}{5}\right) \div\left(\frac{2}{5}-\frac{1}{3}\right)\)
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