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Math Help - Find an equation for the line...

  1. #1
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    Post Find an equation for the line...

    I am having trouble studying for my Algebra final. I am having problems giving equations for lines. The two problems that I am currently stuck on are--

    (1) Give an equation for the horizontal through the point (2,3). (Is this wanting y=mx + b formula??)

    and

    (2) Find an equation for the line perpendicular to 2x + 5y = 10 and passes through (-2, 3) from (-1,3) (I think you do something with a negative reciprocal maybe, but I don't know where to begin)

    Thank you in advance for your help!

    Ashley
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  2. #2
    A riddle wrapped in an enigma
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    Quote Originally Posted by aperkin2 View Post
    I am having trouble studying for my Algebra final. I am having problems giving equations for lines. The two problems that I am currently stuck on are--
    Quote Originally Posted by aperkin2 View Post

    (1) Give an equation for the horizontal through the point (2,3). (Is this wanting y=mx + b formula??)
    Hi Ashley,

    A horizontal line will always take the form y = b, where b is the y-intercept. Remember, the slope of a horizontal line is 0. Your y-intercept will be the y coordinate of your point.

    Quote Originally Posted by aperkin2 View Post

    (2) Find an equation for the line perpendicular to 2x + 5y = 10 and passes through (-2, 3) from (-1,3) (I think you do something with a negative reciprocal maybe, but I don't know where to begin)
    Here, you have to find the slope of the line defined by 2x + 5y = 10. A little manipulation of this equation will get it into the slope-intercept form:

    y=-\frac{2}{5}x+2

    Recognize that the slope is -\frac{2}{5}

    The slope of a perpendicular will be the negative reciprocal of this slope. That is, we invert the fraction and change its sign. This slope becomes:

    m=\frac{5}{2}

    Now, this is where I'm having difficulty understanding which line you are trying to define.

    What do you want to do? Are we defining a line perpendicular to 2x + 5y = 10 from (-2, 3) or are we defining a line perpendicular to 2x + 5y = 10 from (-1, 3)? Or is it something else entirely?
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