Friday, July 31, 2009

How do i write an equation of a line in standard form that has a slope of -3/5 and passes through (2,1)?

i no standard form is Ax+By=C, but how do i make it happen?

How do i write an equation of a line in standard form that has a slope of -3/5 and passes through (2,1)?
hey dont worry i ll help u out......





given pt. is (2,1) and the slope is -3/5.


so the eqn. of the line is-





(y-1)=-3/5(x-2)


solve it and u ll get,





3x+5y=11 (answer)
Reply:1 = (-3/5)(2) + b.


b = 11/5.





Equation in slope-intercept form: y = -3x/5 + 11/5.





Equation in standard form: 3x + 5y = 11.





-John
Reply:gradient = -3/5 and point (2,1)





use equation y-y1=m(x-x1)


where m is the gradient and point (2,1) is( x1,y1)


therefore substitute in eqn:


(y-1)=-3/5(x-2)


y-1=3/5x-6/5


y=3/5x-1/5


5y=3x-1
Reply:You write





y = (-3/5) (x) + b





and determine b from the given point (2, 1) on the line; then rewrite the line equation given above with b replaced.





If you want a standard form with all variable terms on the left and a constant on the right, then you can juggle the above expression (after determining b) and get to that form.
Reply:start with point-slope form





(y-1) = (-3/5)(x-2)





multiply through by 5





5y - 5 = -3x + 6





add 5 to both sides





5y = -3x + 11





add 3x to both sides





5y + 3x = 11
Reply:Us the point-slope form





y - 1 = (-3/5)(x - 2)





Multiply both sides by 5





5y - 5 = -3(x - 2)





Multiply through the -3





5y - 5 = -3x + 6





Add 3x to both sides





3x + 5y - 5 = -3x + 3x + 6





3x + 5y - 5 = 6





Add 5 to both sides





3x + 5y - 5 + 5 = 6 + 5





3x + 5y = 11
Reply:(2,1) are the x and y coordinates. (x,y)





Equation of a line is in the form:





y= mx + c, where,


m is the gradient or slope of the line


c is the y-intercept





"m" is known as -3/5





Next find y-intercept.


substitue into the general form: y = mx+c





we use co-ordinate (2, 1)





1 = -3/5 (2) + c


5/5 = -6/5 + c


c = 11/5





Now, we have m = -3/5 and c = 11/5





Hence, general equation of the line is





y = -3/5x + 11/5





multiply 5 on both sides:





5y = -3x +11





Re-arranging equation:





3x + 5y = 11


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