A new LED light bulb uses 10 watts of power. Since energy
=
power
×
time
, then the energy used for this light bulb can be found my multiplying the power times the time the bulb is lit. If the bulb is lit for one hour, the energy used will be 10 watt*hours or 10 Wh. If three 10 watt bulbs in one room are kept on for 5 hours, how many watt*hours of energy are used?

Parents sometimes yell at their children for leaving the light on in their bedroom when they aren't in the room. If the child's room is lit with two 10 watt bulbs for one extra hour a day for everyday of the year (365), and the cost of energy is $0.068 per kilowatt*hour (kWh), how much money is wasted on lighting that isn't being used, to the nearest cent.

150 Wh

I guess the question means, how much money is wasted on lighting in a year ?

$0.50

Step-by-step explanation:

3 × 10W × 5 hours = 150 Wh

2 × 10W × 1 hour × 365 × 0.068 / 1000

divided by 1000, because the price is in kWh (1000 Wh), but the rest of the calculation refers to W. so, we need to bring all factors to the same dimension. the division by 1000 either brings the Wh to kWh, or the price to the price for Wh (instead of kWh). it does not matter which one. just one of these 2 things have to happen here, so that all factors have the same dimension.

=> 20 × 365 × 0.068 / 1000 = 7300 × 0.068 / 1000 =

= 7.3 × 0.068 = $0.50 (rounded from 0.4964)

step-by-step explanation:

i dont get

the first one is x^2+2x+2

the second one is x^2+4

the last one is x^2-4x+8