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: 22

Answer

The solutions are $(-1, 0)$ and $(-2, 0)$.

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: $-x^2 - 3x - 2 = x^2 + 3x + 2$ We want to move all terms to the left side of the equation. First, we will subtract $x^2$ from both sides of the equation: $-2x^2 - 3x - 2 = 3x + 2$ Subtract $3x$ from both sides of the equation: $-2x^2 - 6x - 2 = 2$ Subtract $2$ from both sides of the equation: $-2x^2 - 6x - 4 = 0$ Factor out common terms: $-2(x^2 + 3x + 2) = 0$ Divide each side by $-2$: $x^2 + 3x + 2 = 0$ Factor the quadratic equation. The factors $2$ and $1$ will work: $(x + 2)(x + 1) = 0$ Set each factor equal to $0$. First factor: $x + 2 = 0$ Subtract $2$ from each side of the equation: $x = -2$ Second factor: $x + 1 = 0$ Subtract $1$ from each side of the equation: $x = -1$ 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: $y = (-1)^2 + 3(-1) + 2$ Evaluate the exponent first: $y = 1 + 3(-1) + 2$ Multiply next: $y = 1 - 3 + 2$ Add or subtract from left to right: $y = 0$ Let's solve for $y$ using the other solution for $x$: $y = (-2)^2 + 3(-2) + 2$ Evaluate the exponent first: $y = 4 + 3(-2) + 2$ Multiply next: $y = 4 - 6 + 2$ Add or subtract from left to right: $y = 0$ The solutions are $(-1, 0)$ and $(-2, 0)$.
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