Put the Variable in ParenthesesDate: 10/15/2001 at 07:39:38 From: John Greaney Subject: Quadratic functions plotting the parabola For the equation y = x^2 + x - 6 range -4 to 3 I get the following coordinates: x -4 -3 -2 -1 0 1 2 3 y -26 -18 -12 -9 -6 -4 0 6 The answers and the graph in my book look totally different. Here is some of my working out: x= -4 therefore -4 sqd-4-6 = -16-4-6 = -26 Am I on the right track? Thanks, John Date: 10/15/2001 at 12:52:01 From: Doctor Peterson Subject: Re: Quadratic functions plotting the parabola Hi, John. Be careful multiplying negative numbers! Remember that the square of -4 is -4 * -4, which is the positive number 16, not -16. Perhaps you confusing yourself by writing the expression down without thinking about the order of operations. You need to write 2 (-4) + (-4) - 6 = 16 - 4 - 6 = 6 If you wrote 2 -4 + -4 - 6 = -16 - 4 - 6 = -26 you did not write what you really meant, because this says to square 4 and then take the negative of the result, which is different from squaring -4. I recommend always putting the value of the variable in parentheses, to ensure that it is kept together when you evaluate it, rather than ripping the minus sign off as you did. - Doctor Peterson, The Math Forum http://mathforum.org/dr.math/ |
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