4x=7-5y
8x=9-5y
2007-02-22 22:30:57 · 6 answers · asked by tony t 1 in Science & Mathematics ➔ Mathematics
4x=7-5y------> 4x+5y=7
8x=9-5y------> 8x+5y=9
solve x by elimination
-1(4x+5y=7)
8x+5y=9
~>
-4x-5y=-7
8x+5y=9
------------------
4x=2
4x/4=2/4
x=2/4 or 1/2
solve for y(i used the 2nd equation)
8x+5y=9
~>
8(1/2)+5y=9
5y=9-4
5y=5
5y/5=5/5
y=1
2007-02-22 23:33:13 · answer #1 · answered by jAmPr0tzz 2 · 1⤊ 0⤋
If you substract those equations you get:
8x - 4x = (9-5y) - (7-5y)
=> 4x = 9 - 5y - 7 + 5y
So 4x = 2 => x=1/2
Then replace x in one equation: 8*1/2 = 4 = 9 - 5y
=> y=1
2007-02-22 22:35:28 · answer #2 · answered by jspiar 1 · 1⤊ 0⤋
Add 5y from both sides on both equations:
4x+5y=7
8x+5y=9
Multiply the first equation by -1:
-4x-5y=-7
8x+5y=9
=======
4x=2
x=1/2
8(1/2)+5y=9
4+5y=9
5y=5
y=1
The solution set is (1/2,1)
Check:
4(1/2)=7-5(1)
2=7-5
2=2
8(1/2)=9-5(1)
4=9-5
4=4
I hope this helps!
2007-02-23 01:19:51 · answer #3 · answered by Anonymous · 0⤊ 0⤋
4x=7-5y ---- (1)
8x=9-5y ---- (2)
(2)-(1): 4x=2 ==> x=1/2 ---- (3)
(3) into (1): 4(1/2)=7-5y ==> 2-7=-5y ==> -5=-5y ==> y=1
2007-02-23 03:24:00 · answer #4 · answered by nieteni 2 · 0⤊ 0⤋
Get equations into standard form with at least one variable having the same coefficient in both equations
14=8x+10y
-9=-8x-5y
add the equations (or subtract)
5=5y
so y=1, then plug y into one of the top equations.
4x=7-5*1
4x=2
x=2
2007-02-23 00:40:30 · answer #5 · answered by MLBfreek35 5 · 0⤊ 0⤋
4x+5y = 7 -------------Equation 1
8x+5y = 9 -------------Equation 2
----------
Multiply Equation 1 with -1
-4x-5y = -7
8x+5y = 9
----------
4x = 2
x = 0.5
-------
2+5y = 7
5y = 5
y = 1
-------
Ans: X = 0.5
Y = 1
2007-02-22 22:37:12 · answer #6 · answered by GURU 3 · 1⤊ 0⤋