Ch. 3 - Polynomial and Rational Functions

Lial13th EditionCollege AlgebraISBN: 9780136881063Not the one you use?Change textbook

Lial 13th Edition

Ch. 3 - Polynomial and Rational Functions

Problem 13

Chapter 4, Problem 13

Solve each problem. Suppose r varies directly as the square of m, and inversely as s. If r=12 when m=6 and s=4, find r when m=6 and s=20.

Verified step by step guidance

Identify the relationship given: r varies directly as the square of m and inversely as s. This can be written as the equation \(r = k \frac{m^2}{s}\), where \(k\) is the constant of proportionality.

Use the given values \(r=12\), \(m=6\), and \(s=4\) to find the constant \(k\). Substitute these values into the equation: \(12 = k \frac{6^2}{4}\).

Simplify the expression inside the fraction: \(6^2 = 36\), so the equation becomes \(12 = k \frac{36}{4}\).

Solve for \(k\) by multiplying both sides by 4 and then dividing by 36: \(k = \frac{12 \times 4}{36}\).

With \(k\) found, substitute \(m=6\) and \(s=20\) into the original formula \(r = k \frac{m^2}{s}\) to find the new value of \(r\).

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Direct Variation

Direct variation describes a relationship where one variable is proportional to another. In this problem, r varies directly as the square of m, meaning r increases as m² increases, expressed as r ∝ m².

Inverse Variation

Inverse variation means one variable changes in the opposite way to another. Here, r varies inversely as s, so as s increases, r decreases proportionally, represented as r ∝ 1/s.

Formulating and Solving Variation Equations

To solve, combine direct and inverse variations into an equation: r = k * (m²) / s, where k is a constant. Use given values to find k, then substitute new values of m and s to find r.

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Use synthetic division to divide ƒ(x) by x-k for the given value of k. Then express ƒ(x) in the form ƒ(x)=(x-k)q(x)+r. ƒ(x)=-3x³+5x-6; k=-1

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Use synthetic division to divide ƒ(x) by x-k for the given value of k. Then express ƒ(x) in the form ƒ(x)=(x-k)q(x)+r. ƒ(x)=5x³-3x²+2x-6; k=2