Simultaneous equations (1 Viewer)

[MrBrightside]

solve simultaneously:

xy = 4 and 2x - y - 7 = 0

its the xy part that makes in confusing for me, how do you separate them? is make x = 0 to find y and y = 0 to find x? help is appreciated thx.

 

[SeCKSiiMiNh]

y = x/4

then sub it into the other one

 

[tommykins]

y = x/4

then sub it into the other one

what

xy = 4, 2x-y = 7
y = 4/x

2x-4/x = 7

multiply by x and solve

 

[SeCKSiiMiNh]

what

xy = 4, 2x-y = 7
y = 4/x

2x-4/x = 7

multiply by x and solve

oh yeah, its the other way around.lol

 

[thongetsu]

lol yeah you had it mixed up.

so it'd be 2x^2 +7x -4 = 0
(x+4)(2x-1)=0
x=-4,1/2

 

[FrasbR]

xy = 4
2x-y-7 = 0

y = 4/x
y=2x-7

2x-7 = 4/x
2x^2-7x = 4
2x^2-7x-4 = 0

(2x+1)(x-4) = 0

x = 4, y = 1
or
x = -0.5, y = -8

 

[hscishard]

lol yeah you had it mixed up.

so it'd be 2x^2 +7x -4 = 0
(x+4)(2x-1)=0
x=-4,1/2

Think you misinterpreted the question.

Should be 2x^2 - 7x -4

 

[thongetsu]

oops