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Find the equation for the parabola with focus at (-1,1) and vertex at (4,1)
\n" ); document.write( "The focus S(-1,1) and the vetex A(4,1) are on the line y =1 which is a horizontal line parallel to the x-axis at a distance 1 unit above it
\n" ); document.write( "Axis horizontal means the parabola is square in y and linear in x
\n" ); document.write( "The focus is to the left of the vertex, which means the parabola is facing west
\n" ); document.write( "The equation to the parabola will be of the form
\n" ); document.write( "(y-k)^2 = -4a(x-h)----(1)
\n" ); document.write( "Where A(h,k ) = A(4,1) and a = distance of the focus from the vertex.
\n" ); document.write( "The distance SA = (one unit to the y-axis plus 4 units to the vertex) = 1+4 = 5
\n" ); document.write( "Therefore putting h =4, k = 1 and a = 5
\n" ); document.write( "Therefore (1) becomes
\n" ); document.write( "(y-1)^2 = -4X5(x-4)
\n" ); document.write( "(y-1)^2 = -20(x-4)
\n" ); document.write( "y^2-2y+1= -20x+80
\n" ); document.write( "y^2-2y+20x+1-80 =0
\n" ); document.write( "y^2-2y+20x-79 = 0
\n" ); document.write( "Answer:y^2-2y+20x-79 = 0
\n" ); document.write( "--------------------\r
\n" ); document.write( "\n" ); document.write( "which DOES NOT tally with any of the following given answers:
\n" ); document.write( "(A) x^2-8x+20y+28=0
\n" ); document.write( "(B) x^2-8x+20y+12=0
\n" ); document.write( "(C) y^2-2y+20x+81=0
\n" ); document.write( "(D) y^2+2y+20x-79=0\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Remark: Either the set of answers given is wrong or the given particulars about the parabola are wrong. Please give the correct problem \r
\n" ); document.write( "\n" ); document.write( " \n" ); document.write( "