–4x + 7y = –10
x – 5y = 9
2006-09-03 18:20:50 · 8 answers · asked by envymisskrayz_05 1 in Science & Mathematics ➔ Mathematics
Multiply the second equation by 4 and then add that to the first equation (you do this so that the x's will cancel)
-4x + 7y = -10
4x - 20y = 36
Add the two above equations to get
-13y = 26
Divide both sides by -13
y = -2
Now replace y with -2 in either one of the original equations.
x - 5(-2) = 9
x + 10 = 9
x = -1
Answer: (-1,-2)
2006-09-03 18:24:16 · answer #1 · answered by MsMath 7 · 0⤊ 0⤋
x - 5y = 9
x = 9 + 5y (when change side, "-" become "+")
subsitute x = 9 + 5y to -4x + 7y = -10
-4(9 + 5y) + 7y = -10
-36 - 20y + 7y = -10
-13y = -10 +36
-13y = 26
y = 26/-13
y = -2
substitute y = -2 to x = 9 + 5y
x= 9 + 5(-2)
x = 9 -10
x = -1
checking -4x + 7y = -10
-4(-1) + 7(-2)
= 4 -14
= -10
checking x - 5y = 9
(-1) - 5(-2)
= -1 + 10
= 9
therefore x = -1, y = -2
2006-09-04 01:39:04 · answer #2 · answered by evelyn_01 3 · 0⤊ 0⤋
add the equasions
-4x + 7y = -10
x - 5y = 9
-------------------------------
-3x + 2y = -1
take the sum
-3x + 2y = -1 and solve for x or y
2y = -1+3x
y = -(1/2) + (3/2)x
plug y into one of the first equasions
x-5y=9
x-5 (-1/2 + 3/2 x) = 9
solve for x
x + 5/2 + 15/2 x = 9
17/2 x = 9 - 5/2
x = (9 - 5/2) times 2/17 (get out the calculator)
when you have x.....plug it in any equasion and solve for y
2006-09-07 18:59:19 · answer #3 · answered by answerer 2 · 0⤊ 0⤋
-4x + 7y= -10
x - 5y = 9
4(x - 5y = 9)
-4x +7y = -10
4x - 20y = 36
-13y = 26
y = -2
-4x + 7(-2) = -10
-4x - 14 = -10
-4x = 4
x = -1
2006-09-04 01:36:00 · answer #4 · answered by Poetic Justice 1 · 0⤊ 0⤋
x=9+5y
Now substitute for x in the first equation:
-4(9+5y) + 7y = -10
-36-20y + 7y = -10
-13y = 26
y=-2
Then substitute for y:
x-5(-2)=9
x+10=9
x=-1
2006-09-04 01:27:09 · answer #5 · answered by Jim S 5 · 0⤊ 0⤋
y=-2, x=-1
2006-09-04 01:29:09 · answer #6 · answered by naas- just feel it 4 · 1⤊ 0⤋
Yeah x = -1. y = -2
2006-09-04 01:46:30 · answer #7 · answered by Bartimaeus™ 5 · 0⤊ 0⤋
-4x+7y=-10
4x-20y=36
adding
-13y=26
y=-2
substituting
x=-1
2006-09-04 01:24:29 · answer #8 · answered by raj 7 · 0⤊ 0⤋