y = 3x 5x - 4y = 21 The system of equations above has solution (x, y). What is the value of x + y?
llm
Answered on
Given:
y = 3x
5x - 4y = 21
Solve x + y
Solution:
In order to solve for x and y, we substitute first the first equation to the second equation in order to determine the value of x.
y = 3x
5x - 4 (3x) = 21
5x - 12x = 21
-7x = 21
Divide both sides by -7 in order to cancel out -7x leaving behind x.
-7x/-7 = 21/-7
x = -3
Substitute the value of x to the equation of y.
y = 3(-3)
y = -9
Solve for x + y
= x + y
= -3 + ( - 9)
= -3 - 12
= - 15
Final answer:
= -15