How do you solve -2x-9y=-25 and -4x-9y=-23?
2 Answers
I found:
Explanation:
I would add together the two equations (in columns) after multiplying the first by
Substitute into the first equation:
Explanation:
Your system of equations looks like this
#{(-2x-9y = -25), (-4x-9y = -23) :}#
Multiply the first equation by
#-2x-9y = -25| * (-1)#
#2x + 9y = 25#
The system now looks like this
#{(2x+9y = 25), (-4x-9y = -23) :}#
Add the left-hand sides and the right-hand sides of the two equations seprately to get
#2x + color(red)(cancel(color(black)(9y))) - 4x - color(red)(cancel(color(black)(9y))) = 25 - 23#
#-2x = 2 implies x= 2/((-2)) = -1#
Take this value of
#-2 * (-1) - 9y = -25#
#2 - 9y = -25#
#-9y = -27 implies y = ((-27))/((-9)) = 3#
The solution set to this system of equations is