Question 67784
please help to solve
x + 3y = 7
Solve for x:
x = (7 - 3y)
:
Substitute (7-3y) for x in:
xy = 2
:
(7-3y) * y = 2
:
7y - 3y^2 = 2
:
Arrange as a quadratic equation:
-3y^2 + 7y - 2 = 0
:
Easier to factor if the 3y^2 is positive, multiply equation by -1
3y^2 - 7y + 2 = 0
:
Factors to:
(3y-1)(y-2) = 0
:
Two solutions for y
3y = +1
y = (1/3)
and
y = +2
:
Find the value of x using y = (1/3):
x + 3y = 7
x + 3(1/3) = 7
x + 1 = 7 - 1
x = +6
:
Find the value of x using y = 2
x + 3y = 7
x + 3(2) = 7
x + 6 = 7
x = 7 - 6
x = +1
:
We have two solution coordinates. x = 6: y =(1/3) and x = 1, y = 2
:
Note that both will satisfy the xy = 2 equation
:
Graphing you can see this is true also:
{{{ graph( 300, 200, -2, 8, -2, 6, 2/x, (7/3)-(x/3)) }}}
:
you can see they intersect and 6,(1/3) and 1,2
:
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