Algebra 2 Common Core

Published by Prentice Hall
ISBN 10: 0133186024
ISBN 13: 978-0-13318-602-4

Chapter 4 - Quadratic Functions and Equations - 4-9 Quadratic Systems - Practice and Problem-Solving Exercises - Page 262: 23

Answer

$(0, -3)$ and $\left(\frac{1}{3}, -\frac{31}{9}\right)$

Work Step by Step

We will use substitution to solve this system of equations. We substitute one of the expressions for $y$, which would mean that we are going to set the two equations equal to one another to solve for $x$ first: $-x^2 - x - 3 = 2x^2 - 2x - 3$ We want to move all terms to the left side of the equation. First, we will subtract $2x^2$ from both sides of the equation: $-3x^2 - x - 3 = -2x - 3$ Add $2x$ to both sides of the equation: $-3x^2 + x - 3 = -3$ Add $3$ to both sides of the equation: $-3x^2 + x = 0$ Factor out common terms: $x(-3x + 1) = 0$ Set each factor equal to $0$. First factor: $x = 0$ Second factor: $-3x + 1 = 0$ Subtract $1$ from each side of the equation: $-3x = -1$ Divide each side of the equation by $-3$: $x = \frac{1}{3}$ Now that we have the two possible values for $x$, we can plug them into one of the original equations to find the corresponding $y$ values. Let's use the first equation: $y = (-0)^2 - (0) - 3$ Evaluate the exponent first: $y = 0 - 0 - 3$ Add or subtract from left to right: $y = -3$ Let's solve for $y$ using the other solution for $x$: $y = (\frac{1}{3})^2 - (\frac{1}{3}) - 3$ Evaluate the exponent first: $y = \frac{1}{9} - (\frac{1}{3}) - 3$ Multiply next: $y = \frac{1}{9} - \frac{1}{3} - 3$ Find equivalent fractions with common denominators to add the fractions together: $y = \frac{1}{9} - \frac{3}{9} - \frac{27}{9}$ Add or subtract from left to right: $y = -\frac{31}{9}$ The solutions are $(0, -3)$ and $\left(\frac{1}{3}, -\frac{31}{9}\right)$.
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