For y=x^2-6x-11
complete the square
so roots
set y=0
0=x^2-6x-11
group x terms
0=(x^2-6x)-11
take 1/2 of linear coefient (-6) and square it
-6/2=-3, (-3)^2=9
add positive and neative to inside of parenthasees
0=(x^2-6x+9-9)-11
complete square
0=((x-3)^2-9)-11
expand
0=(x-3)^2-9-11
0=(x-3)^2-20
add 20 to both sides
20=(x-3)^2
sqrt both sides
remember positive and negative roots
+/-2√5=x-3
add 3 to both sides
3+/-2√5=x
so
x=3+2√5 and 3-2√5
You would have 14.76 trees cut
Equation 1.
20÷4=5
0×3=0
5-5=0
Equation 2.
44÷4=11
2×3=6
11-5=6
Equation 3.
56÷4=14
3×3=9
14-5=9
-3/6 = -1/2 is the slope of the line.
A 120 watt light-bulb is a 0.120 kilowatt light bulb.
In one hour, it uses 0.120 kilowatt-hour of energy.
If electrical energy costs $0.20 per kilowatt hour, then that light bulb costs
(0.120 kilowatt-hour / hour) x (0.20 dollar / kilowatt-hour) =
(0.120 x $0.20 / hour) =
$0.024 / hour = <span>2.4¢ per hour </span>
