Algebra 2 (1st Edition)

Published by McDougal Littell
ISBN 10: 0618595414
ISBN 13: 978-0-61859-541-9

Chapter 4 Quadratic Functions and Factoring - 4.10 Write Quadratic Functions and Models - 4.10 Exercises - Skill Practice - Page 313: 30

Answer

See below

Work Step by Step

The standard form of the equation is: $y=ax^2+bx+c$ Given three points: $(-4,-6)\\(0,-2)\\(2,6)$ Substitute: $-6=a(-4)^2+b(-4)+c\\-2=a(0)^2+b(0)+c\\6=a(2)^2+b(2)+c$ We have the system: $16a-4b+c=-6\\c=-2\\4a+2b+c=6$ Substitute $c$ into the equations, we have: $16a-4b=-4\\4a+2b=8$ Multiply the second equation with $2$ and add to the first equation: $24a=12\rightarrow a=\frac{1}{2}$ Substitute $a$ into the second equation: $4(\frac{1}{2})+2b=8\\ 2b=6\\\rightarrow b=3$ Hence, $a=\frac{1}{2}\\b=3\\c=-2$ Substitute back to the initial equation: $y=\frac{1}{2}x^2+3x-2$
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