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The Watercooler
E needs algebra help again
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<blockquote data-quote="Kathy813" data-source="post: 550408" data-attributes="member: 1967"><p>Good job, Tedo. I couldn't have done it better myself.</p><p></p><p>To find the vertex, you use the equation x = -b/2a (or in this case: k = -b/2a).</p><p></p><p>f(k) = k^2-14k-51</p><p></p><p>a=1; b = -14; k = -51</p><p></p><p>So for the vertex:</p><p></p><p>k = -(-14)/2(1)</p><p>k=14/2</p><p>k=7</p><p></p><p>Then subsitute the k value (7) into the equation for k and that will give you the y-value of the vertex.</p><p></p><p>f(7) = (7)^2 - 14(7) - 51</p><p>f(7) = -100</p><p></p><p>Therefore, the vertex is at (7, -100).</p><p></p><p>There is more than one way to do this. You could also use completing the square to change the equation into vertex form and find the vertex that way. I don't know if he is allowed to use a graphing calculator but you could also find the vertex by using the second trace function on the calculator. Still another method if you know the x-intercepts (which you do in this case) is to take the two x-values, add them together and divide by two since the vertex will fall halfway between them. Then do the second step above.</p><p></p><p>Is your head spinning yet? LOL</p><p></p><p>I love math!!</p></blockquote><p></p>
[QUOTE="Kathy813, post: 550408, member: 1967"] Good job, Tedo. I couldn't have done it better myself. To find the vertex, you use the equation x = -b/2a (or in this case: k = -b/2a). f(k) = k^2-14k-51 a=1; b = -14; k = -51 So for the vertex: k = -(-14)/2(1) k=14/2 k=7 Then subsitute the k value (7) into the equation for k and that will give you the y-value of the vertex. f(7) = (7)^2 - 14(7) - 51 f(7) = -100 Therefore, the vertex is at (7, -100). There is more than one way to do this. You could also use completing the square to change the equation into vertex form and find the vertex that way. I don't know if he is allowed to use a graphing calculator but you could also find the vertex by using the second trace function on the calculator. Still another method if you know the x-intercepts (which you do in this case) is to take the two x-values, add them together and divide by two since the vertex will fall halfway between them. Then do the second step above. Is your head spinning yet? LOL I love math!! [/QUOTE]
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E needs algebra help again
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