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finding the equation of a perpendicular line watch

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    Ok, so I fixed the quadratics to get this:
    (x-2)(2x-1)=0
    which meant that x was equal to 2 and 1/2.

    Which equation do I substitute the (I assume) 1/2 into?
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    (Original post by frostyy)
    Ok, so I fixed the quadratics to get this:
    (x-2)(2x-1)=0
    which meant that x was equal to 2 and 1/2.

    Which equation do I substitute the (I assume) 1/2 into?
    You can substitute them into either equation and they will return the same y value (after all, the points appear on both lines). You've got x=0.5 and x=2. What does this mean? Well, it means you've got your x coordinates for points A and B respectively. To find the y coordinates you just plug these values back in (doesn't matter which equation as the answer should be the same). You should then get a pair of answers.

    When x = 2, y = ?
    When x = 0.5, y = ?

    Well, we know that point B is (2,8) because you wrote that down already in the original picture. We can confirm this by substitution. Recall that the equations of the lines are \displaystyle y=2x^2 and \displaystyle y=5x-2. Now for the check: \displaystyle 2(2)^2=8 and \displaystyle 5(2)-2=8. So (2,8) is a point that appears on both lines indeed. Now you need to find the y coordinate when x = 0.5. And remember, it doesn't matter which equation you substitute that into because the answer should be the same.
 
 
 
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