7.
a(0,3) b(3,0)
x1 = 0, y1 = 3
x2 = 3, y2 = 0
formula :
[tex]\displaystyle \frac{y-y1}{x-x1} =\frac{y2-y1}{x2-x1}[/tex]
[tex]\displaystyle \frac{y-3}{x-0} =\frac{0-3}{3-0}[/tex]
[tex]\displaystyle \frac{y-3}{x} =\frac{-3}{3}[/tex]
[tex]\displaystyle 3(y-3) = -3x[/tex]
[tex]\displaystyle 3y - 9 = -3x\\ \\ \\ 3y= -3x+9\\ \\ \\ we\ divide\ both\ side\ by\ \\ \\ \\ >>> y = -x+3[/tex]
8.
a(1,1) b(0,-4)
x1 = 1, y1 = 1
x2 = 0, y2 = -4
the same formula as number 7 :
[tex]\displaystyle \frac{y-y1}{x-x1} =\frac{y2-y1}{x2-x1}[/tex]
[tex]\displaystyle \frac{y-1}{x-1} =\frac{-4-1}{0-1}[/tex]
[tex]\displaystyle \frac{y-1}{x-1} =\frac{-5}{-1}[/tex]
[tex]\displaystyle -1(y-1) = -5(x-1)[/tex]
[tex]\displaystyle -y+1 = -5x+5[/tex]
[tex]\displaystyle -y= -5x+4[/tex]
[tex]\displaystyle >>> y= 5x-4[/tex]
