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Elis [28]
3 years ago
13

If x + y = 7 and xy = 4, then find the value of x^2 + y^2.

Mathematics
2 answers:
Evgen [1.6K]3 years ago
6 0
X+y=7
xy=4

in xy=4, divide both sides by any variable (lets say i divide it y y)
xy=4
x=4/y
Now substitute it to the 1st equation
x+y=7
4/y+y=7
Multiply both sides by y
4+y^2=7y
Change to standard form
y^2-7y=4
Use the square of something...
y^2-7y+49/4=4+49/4
(y+7/2)^2=65/4
Squareroot both sides
y+7/2=posinega(sqrt of 65)/2
y=(sqrt of 65)/2-7/2
or y=-(sqrt of 65)/2-7/2
babunello [35]3 years ago
3 0

I don't know really how to do this stuff but I have learned in 7th grade and still working on it.

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What is the solution set for the following system of equations 5x-3y-10=0 x+y-7=0
garik1379 [7]

(x, y) = ( \frac{31}{8}, \frac{25}{8})

given the 2 equations

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