document.write( "Question 774982: find an equetion of parabola with the axis is parallel to y-axis & the parabola passes through (-4,21),(-2,11),(4,5) \n" ); document.write( "
Algebra.Com's Answer #473688 by lwsshak3(11628)\"\" \"About 
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find an equation of parabola with the axis is parallel to y-axis & the parabola passes through (-4,21),(-2,11),(4,5)
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\n" ); document.write( "General form of equation for a parabola:
\n" ); document.write( "y=ax^2+bx+c
\n" ); document.write( "..
\n" ); document.write( "(-4,21), 21=16a-4b+c
\n" ); document.write( "(-2,11), 11=4a-2b+c
\n" ); document.write( "(4,5),.... 5=16a+4b+c
\n" ); document.write( "..
\n" ); document.write( "21=16a-4b+c
\n" ); document.write( " 11=4a-2b+c
\n" ); document.write( "subtract to eliminate c
\n" ); document.write( "10=12a-2b
\n" ); document.write( "..
\n" ); document.write( "11=4a-2b+c
\n" ); document.write( "5=16a+4b+c
\n" ); document.write( "subtract to eliminate c
\n" ); document.write( "6=-12a-6b
\n" ); document.write( "..
\n" ); document.write( "10=12a-2b
\n" ); document.write( "6=-12a-6b
\n" ); document.write( "add to eliminate a
\n" ); document.write( "16=-8b
\n" ); document.write( "b=-2
\n" ); document.write( "12a=10+2b=10-4=6
\n" ); document.write( "a=6/12=1/2
\n" ); document.write( "c=11-4a+2b=11-2-4=5
\n" ); document.write( "..
\n" ); document.write( "a=1/2, b=-2, c=5
\n" ); document.write( "Equation: y=(1/2)x^2-2x+5 \n" ); document.write( "
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