Solve the system of linear equations by substitution. x + 4y = 30
y = −x + 9

The solution of the system is (___, ___).

hey! This was the only part of mathematics I ever enjoyed! So consider this both of our lucky days: Answer is : (2,7)

Step-by-step explanation:

basically plug in Y to the first equation as sox + 4(-x + 9) = 30

x - 4x + 36 = 30- 3x = - 6

x = 2

then plug that in to Y!

Y = -(2) + 9

so Y = 7

and our answer is : (2,7)

(b) 240

step-by-step explanation:

first, we use the pythagorean formula using the given side lengths to find x. then we use x to find the side lengths. then we add the side lengths to find the perimeter.

pythagorean theorem formula:

a^2 + b^2 = c^2

(x - 20)^2 + (x - 40)^2 = x^2

x^2 - 40x + 400 + x^2 - 80x + 1600 = x^2

x^2 -120x + 2000 = 0

(x - 100)(x - 20) = 0

x - 100 = 0 or x - 20 = 0

x = 100 or x = 20

we see that the solution x = 20 must be discarded because it will give a negative side length and a side length of 0. the only valid solution is x = 100.

perimeter = sum of the lengths of the sides

perimeter = x + x - 20 + x - 40

perimeter = 3x - 60

replace x with 100.

perimeter = 3(100) - 60

perimeter = 300 - 60

perimeter = 240