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 263: 51

Answer

The solution is $\left(\frac{1}{2}, \frac{7}{2}\right)$.

Work Step by Step

We will use substitution to solve this system of equations. We substitute one of the expressions given for the $y$ term, which would mean that we are going to set the two equations equal to one another to solve for $x$ first: $-4x^2 + 7x + 1 = 3x + 2$ We want to move all terms to the left side of the equation: $-4x^2 + 7x - 3x + 1 - 2 = 0$ Combine like terms: $-4x^2 + 4x - 1 = 0$ Multiply both sides of the equation by $-1$ so that the $x^2$ term is positive: $4x^2 - 4x + 1 = 0$ Factor the quadratic equation. The quadratic equation takes the form $ax^2 + bx + c = 0$. We need to find factors whose product is $ac$ but that sum up to $b$. In this exercise, $ac = 4$ and $b = -4$. The factors $-2$ and $-2$ will work. Let's split the middle term using these factors: $4x^2 - 2x - 2x + 1 = 0$ Group the first two terms and the last two terms: $(4x^2 - 2x) - (2x - 1) = 0$ Factor out any common terms: $2x(2x - 1) - (2x - 1) = 0$ Group the factors: $(2x - 1)(2x - 1) = 0$ Set the factor equal to $0$: First factor: $2x - 1 = 0$ Add $1$ to each side of the equation: $2x = 1$ Divide each side by $2$: $x = \frac{1}{2}$ Now that we have the value for $x$, we can plug them into one of the original equations to find the corresponding $y$ value. Let's use the second equation: $y = 3x + 2$ Substitute the solution $\frac{1}{2}$ for $x$: $y = 3(\frac{1}{2}) + 2$ Multiply: $y = \frac{3}{2} + 2$ Convert the constant into an equivalent fraction with $2$ as its denominator: $y = \frac{3}{2} + \frac{4}{2}$ Add to solve: $y = \frac{7}{2}$ The solution is $(\frac{1}{2}, \frac{7}{2})$.
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