document.write( "Question 976873: What is the vertex of the quadratic formula y=-x^2+3x+4? I'm trying to do it without a calculator so I can get the vertex every time I try to do a quadratic equation. I've already got the line of symmetry, the y-intercepts, the x-intercepts, the graph, the minimum, the maximum, and the points and I've plotted everything, but two points don't make the vertex a point with whole numbers. If you have a way of getting the vertex of the graph without using a calculator, please let me know. \n" ); document.write( "

Algebra.Com's Answer #598361 by addingup(3677) $\"\"$ $\"About$

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y= -x^2+3x+4 is in the quadratic form y= ax2 + bx + c
\n" ); document.write( "The vertex (h, k) is found by computing h = –b/2a, and then evaluating y at h to find k.
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\n" ); document.write( "h = –b/2a = –(3)/2(1) = –3/2 or -1 1/2, this is one of our vertex points.
\n" ); document.write( "Now we can find k by evaluating y at h= -3/2:
\n" ); document.write( "k= (-3/2)^2+3(-3/2)+4
\n" ); document.write( "= 9/4 -9/2 + 4
\n" ); document.write( "=9/4 - 18/4 + 16/4
\n" ); document.write( "= (9-18+16)/4
\n" ); document.write( "= 7/4 or 1 3/4
\n" ); document.write( "The vertex is at (-1 1/2, 1 3/4)\r
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