document.write( "Question 1085857: find the x-intercepts of the parabola with vertex (-3,16) and y-intercept (0,-20). Write your answer in this form: (x1,y1),(x2,y2). If necessary, round to the nearest hundredth \n" ); document.write( "
Algebra.Com's Answer #699955 by josmiceli(19441)\"\" \"About 
You can put this solution on YOUR website!
The general formula is:
\n" ); document.write( "\"+y+=+a%2Ax%5E2+%2B+b%2Ax+%2B+c+\"
\n" ); document.write( "The formula for the vertex is:
\n" ); document.write( "\"+x%5Bv%5D+=+-b%2F%282a%29+\"
\n" ); document.write( "---------------------------
\n" ); document.write( "You are given 2 points:
\n" ); document.write( "( -3,16 )
\n" ); document.write( "( 0, -20 )
\n" ); document.write( "Plug these values into the general formula
\n" ); document.write( "(-3,16)
\n" ); document.write( "\"+16+=+a%2A%28-3%29%5E2+%2B+b%2A%28-3%29+%2B+c+\"
\n" ); document.write( "\"+9a+-+3b+%2B+c+=+16+\"
\n" ); document.write( "(0,-20)
\n" ); document.write( "\"+-20+=+a%2A0%5E2+%2B+b%2A0+%2B+c+\"
\n" ); document.write( "\"+c+=+-20+\"
\n" ); document.write( "------------
\n" ); document.write( "Now the equation is:
\n" ); document.write( "\"+y+=+a%2Ax%5E2+%2B+b%2Ax+-+20+\"
\n" ); document.write( "Al;so:
\n" ); document.write( "\"+x%5Bv%5D+=+-b%2F%282a%29+\"
\n" ); document.write( "\"+x%5Bv%5D+=+-3+\" ( given )
\n" ); document.write( "\"+-3+=+-b%2F%282a%29+\"
\n" ); document.write( "\"+-b+=+-6a+\"
\n" ); document.write( "\"+b+=+6a+\"
\n" ); document.write( "So, now I have:
\n" ); document.write( "\"+y+=+a%2Ax%5E2+%2B+%286a%29%2Ax+-+20+\"
\n" ); document.write( "also
\n" ); document.write( "\"+y%5Bv%5D+=+16+\" ( given )
\n" ); document.write( "\"+16+=+a%2A%28-3%29%5E2+%2B+%286a%29%2A%28-3%29+-+20+\"
\n" ); document.write( "\"+16+=+9a+-+18a+-+20+\"
\n" ); document.write( "\"+-9a+=+36+\"
\n" ); document.write( "\"+a+=+-4+\"
\n" ); document.write( "and
\n" ); document.write( "\"+b+=+6a+\"
\n" ); document.write( "\"+b+=+-24+\"
\n" ); document.write( "so, the equation is:
\n" ); document.write( "\"+y+=+-4x%5E2+-+24x+-+20+\"
\n" ); document.write( "----------------------------
\n" ); document.write( "Find the roots:
\n" ); document.write( "\"x%5B1%5D+=+%28-b+%2B+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+\"
\n" ); document.write( "\"x%5B1%5D+=+%28-%28-24%29+%2B+sqrt%28+%28-24%29%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+\"
\n" ); document.write( "\"x%5B1%5D+=+%28+24+%2B+sqrt%28+576+-+4%2A%28-4%29%2A%28-20%29+%29%29%2F%282%2A%28-4%29%29+\"
\n" ); document.write( "\"x%5B1%5D+=+%28+24+%2B+sqrt%28+576+-+320+%29%29%2F%28-8%29+\"
\n" ); document.write( "\"x%5B1%5D+=+%28+24+%2B+sqrt%28+256+%29%29%2F%28-8%29+\"
\n" ); document.write( "\"x%5B1%5D+=+%28+24+%2B+16+%29%2F%28-8%29+\"
\n" ); document.write( "\"x%5B1%5D+=+40%2F%28-8%29+\"
\n" ); document.write( "\"x%5B1%5D+=+-5+\"
\n" ); document.write( "----------------
\n" ); document.write( "The other root is at:
\n" ); document.write( "\"+x%5B2%5D+=+%28+24+-+16+%29%2F%28-8%29+\"
\n" ); document.write( "\"+x%5B2%5D+=+8%2F%28-8%29+\"
\n" ); document.write( "\"+x%5B2%5D+=+-1+\"
\n" ); document.write( "The x-intercepts are:
\n" ); document.write( "( -5,0 ) and ( -1,0 )
\n" ); document.write( "-----------------------
\n" ); document.write( "Here's the plot:
\n" ); document.write( "\"+graph%28+400%2C+400%2C+-10%2C+2%2C+-5%2C+20%2C+-4x%5E2+-+24x+-+20+%29+\"
\n" ); document.write( "check the math and get an other opinion if needed\r
\n" ); document.write( "\n" ); document.write( "
\n" ); document.write( "
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