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Home Q & A Board Science-Related Homework Help Mathematics
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datty117 datty117
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11 years ago
Solve the system by the substitution method

x + y = 3

y = x^2 - 7x + 11

The solutions are ?
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wrote...
#1
11 years ago
Since you already have an equation with y alone, substitute that value into the first equation:

x + y = 3

x + (x^2 - 7x + 11) = 3

x^2 - 6x + 11 =3

x^2 - 6x + 8 = 0

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

x= 4 or 2

x + y = 3
y= 3 - x

when x=4
y= 3 - 4
y= -1

when x=2
y= 3 - 2
y= 1

Your answers are (4, -1) and (2, 1)
wrote...
#2
11 years ago
x+x^2-7x+11=3           substitute in y
x^2+-6x+8=0              simplify
(x-4)(x-2)=0                factor
x=4 and 2

y=4^2-7(4)+11            y=2^2-7(2)+11         substitute in x
y=16-28+11               y=4-14+11              simplify
y=-1                          y=1              

SOLUTIONS: (4,-1) and (2,1)
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