I am assuming you wrote the problem wrong. Is it a^2?
A^2 -4A-21=0
(A-7)(A+3)=0
A=7 A=-3, ignore the negative number because it doesn't make sense if you plug in for a.
length=a+3=7+3=10
Width=7=a
What you want to do for each of those is follow the formula, y-y[1]=m(x-x[1]). When I say y[1] and x[1], I mean the x and y values given. So the first one would be y-4=-3(x-(-1)). Then you solve for y by distributing the -3 to x and +1 (+1 because two negatives make a positive), making the equation
y-4=-3x-3. Then you subtract the 4. Answer #1. y=-3x-7.
#2.
y-1=1(x-4)
y-1=x-4
y=x-5
#3.
y-2=2(x-(-1))
y-2=2x+2
y=2x+4
Hope this helped you!
Line point L would be the midpoint of question 3.
