Question 612240
If you are trying to solve a standard quadratic equation of the form:
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{{{ax^2 + bx +c =0}}}
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and you notice that there is no term containing x, then you can use the quadratic formula if you just set b equal to zero. For the example problem you gave:
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{{{4p^2 - 36 =0}}}
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by comparing this to the standard quadratic equation, you can see that a = 4, b = 0, and c = -36. Then by the quadratic formula you can say that:
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{{{p = (-b +- sqrt( b^2-4*a*c ))/(2*a) }}}
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and substituting the values we identified for a, b, and c we get:
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{{{p = (-0 +- sqrt( 0^2-4*4*(-36) ))/(2*4) }}}
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Notice that there is no "b" term before the radical in the numerator. Also there is no b^2 term in the radical. So the numerator is just the radical which is preceded by a + and - sign, and the radical contains just the product -4 times 4 times -36. And the denominator is 2*4  which is 8. So the answer is:
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{{{p = sqrt (-4*4*(-36))/8 }}}
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Doing the multiplication within the radical results in :
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{{{p = sqrt (576)/8 }}}
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The square root of 576 is 24, so the answer becomes:
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{{{p = 24/8 }}}
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And dividing it out results in:
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{{{p = 3}}}
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And don't forget the + and - signs to give you p = +3 and -3.
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But there is even an easier way to do this example problem ... with fewer chances for error because there are less manipulations. Start with the problem as given:
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{{{4p^2 - 36 = 0}}}
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Notice that you can divide both sides (all terms) by 4 to get:
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{{{p^2 - 9 = 0}}}
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Then get rid of the -9 on the left side by adding +9 to both sides as shown:
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{{{p^2 = 9}}}
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Then take the square root of both sides to get the answers:
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{{{p = -3}}} and {{{p = 3}}}
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Hope this helps you to understand the problem a little better.
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