Big Ideas Math - Algebra 1, A Common Core Curriculum

Published by Big Ideas Learning LLC
ISBN 10: 978-1-60840-838-2
ISBN 13: 978-1-60840-838-2

Chapter 9 - Solving Quadratic Equations - 9.5 - Solving Quadratic Equations Using the Quadratic Formula - Exercises - Page 521: 42

Answer

The solutions are $x=2+\sqrt{3}\approx 3.73$ and $x=2-\sqrt{3}\approx 0.27$.

Work Step by Step

The given equation is $\Rightarrow x^2-4x+1=0$ Subtract $1$ from each side. $\Rightarrow x^2-4x+1-1=0-1$ Simplify. $\Rightarrow x^2-4x=-1$ The coefficient of the $x^2-$term is $1$, and the coefficient of the $x-$term is an even number. So, solve by completing the square. $\Rightarrow x^2-4x=-1$ Add $(\frac{b}{2})^2=(\frac{-4}{2})^2=4$ to each side. $\Rightarrow x^2-4x+4=-1+4$ Write the left side as the square of a binomial. $\Rightarrow (x-2)^2=3$ Take the square root of each side. $\Rightarrow x-2=\pm\sqrt{3}$ Add $2$ to each side. $\Rightarrow x-2+2=2\pm\sqrt{3}$ Simplify. $\Rightarrow x=2\pm\sqrt{3}$ The solutions are $x=2+\sqrt{3}\approx 3.73$ and $x=2-\sqrt{3}\approx 0.27$.
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