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 - Problem Solving - Page 314: 46

Answer

See below

Work Step by Step

The standard form of the equation is: $y=ax^2+bx+c$ Given three points: $(0,4)\\(2,3.25)\\(5,3.0625)$ Substitute: $4=a(0)^2+b(0)+c\\3.25=a(2)^2+b(2)+c\\3.0625=a(5)^2+b(5)+c$ We have the system: $c=4\\4a+2b+c=3.25\\25a+5b+c=3.0625$ Substitute $c$ to the two last equations: $4a+2b+4=3.25\\25a+5b+4=3.0625$ We have the new system: $4a+2b=-0.75\\25a+5b=-0.9375$ Add equation (1) to equation (2): $6a=0=-4\\ \rightarrow a=0$ Divide the first equation by $2$ $2a+b=-0.375$ Multiply the first equation by $-5$ and add it to the second equation: $15a=0.9375\\ \rightarrow a=0.0625$ Find $b$: $0.125+b=-0.375\\ \rightarrow b=-0.5$ Hence, $a=0.0625\\b=-0.5\\c=4$ Substitute back to the initial equation: $y=0.0625x^2=0.5x+4$
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