Answer
a) $(0, 42)$, $(5, 55)$, (9, 78)$
b) $a=.35$, $b=.85$, $c=42$
c) 45.1% of households
Work Step by Step
a)
$2003-1998=5$
$2007-1998=9$
b)
$x=0$
$y=ax^2+bx+c$
$42=a*0^2+b*0+c$
$42=a*0+0+c$
$42=0+c$
$42=c$
$x=5$
$y=ax^2+bx+c$
$55=a*5^2+b*5+c$
$55=25a+5b+c$
$55=25a+5b+42$
$55-42=25a+5b+42-42$
$13=25a+5b$
$x=9$
$y=ax^2+bx+c$
$78=a*9^2+b*9+c$
$78=81a+9b+42$
$78-42=81a+9b+42-42$
$36=81a+9b$
$13=25a+5b$
$13-25a=25a+5b-25a$
$13-25a=5b$
$(13-25a)/5=5b/5$
$2.6-5a=b$
$36=81a+9b$
$36=81a+9(2.6-5a)$
$36=81a+23.4-45a$
$36-23.4=36a+23.4-23.4$
$12.6=36a$
$12.6/36=36a/36$
$.35=a$
$2.6-5a=b$
$2.6-5*.35=b$
$2.6-1.75=b$
$.85=b$
c)
$y=ax^2+bx+c$
$y=.35x^2+.85x+42$
$2000-1998=2$
$x=2$
$y=.35x^2+.85x+42$
$y=.35*2^2+.85*2+42$
$y=.35*4+1.7+42$
$y=1.4+43.7$
$y=45.1$
