What is an equation of the line that passes through the point (1,-3) and is perpendicular to the line x+3y=21?

x + 3y =21 equation 1

let the equation perpendicular to X + 3y = 21 be

3x - y + k = 0 equation 2

since the point ( 1 , -3 ) passes through equation 3x - y +k =0

3× 1 - (-3) + k = 0

or, 3 + 3 + k = 0

or, 6 + k =0

or, k = -6

now,

putting the value of k in equation 2

3x - y + k = 0

or, 3x -y -6=0

to find the perimeter of the rectangle this is the expression:

x-9+x-9+3x-4+3x-4=138

if we simplify it:

8x-26=138

remember, 138 is what it all adds up to

the length is 11.5cm

the width is 57.5cm

the area is 661.25cm^2

the answers might not be correct use at own risk