Question 529327
m = -1 is the slope.
so,
y = -x + b
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You can use the point given to find 'b'.
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1 = -2 + b
b = 3
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y  = -x + 3
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That is slope-intercept form.
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Add x to both sides to get:
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x + y = 3
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That is "standard" form of a linear equation.
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In general terms, the "standard form" is:  Ax + By = C, where A, B, and C are constants.
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Done.