An electrician has $120 to spend on interior light fixtures. The wholesale price for a 13-watt low-energy lamp is $4. The price for a high-energy lamp is $5. 1. Write the algebraic expression for how much the electrician spends for a units of the low- energy lamp and b units of the high-energy lamp

we have been given a piecewise function which has three parts

we can graph each part one by one.

first part is x+1 which is just like equation y=x+1

restriction with first part is x< 0 so that means we can use any number for x which is less than 0 for example x=-1 and x=-2

now plug x=-1 into y=x+1 to get y

y=x+1=-1+1=0

so the point will be (-1,0)

similarly we get another point (-2,-1)

now we graph a line joining both points but keep in mind that line must be on left side of x=0 because of restriction x< 0

same way we can graph 2nd and third parts

if we have < or > then we use open circle.

if we have < = or > = then we use close circle.

so using above information, final graph can be drawn as:

there are many, many solutions to this problem.

here are 5 examples:

7555531, 7+5+5+5+5+3+1 = 31

7155553, 7+1+5+5+5+5+3 = 31

7735531, 7+7+3+5+5+3+1 = 31

7375531, 7+3+7+5+5+3+1 = 31

7335931, 7+3+3+5+9+3+1 = 31