document.write( "Question 1086039: If the parabola y_1 = x^2 + 2x + 7 and the line y_2 = 6x + b intersect at only one point, what is the value of b? \n" ); document.write( "
Algebra.Com's Answer #700141 by Fombitz(32388)\"\" \"About 
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If they only intersect at one point then the line is tangent to the parabola at the intersection point.
\n" ); document.write( "Find the derivative of the parabola, the value of the derivative is equal to the slope of the tangent line at that point.
\n" ); document.write( "Find all values where
\n" ); document.write( "\"dy%2Fdx=m=6\"
\n" ); document.write( "For the parabola,
\n" ); document.write( "\"dy%2Fdx=2x%2B2=6\"
\n" ); document.write( "\"2x=4\"
\n" ); document.write( "\"x=2\"
\n" ); document.write( "So then find the value of the parabola when \"x=2\",
\n" ); document.write( "\"y=x%5E2%2B2x%2B7\"
\n" ); document.write( "\"y=%282%29%5E2%2B2%282%29%2B7\"
\n" ); document.write( "\"y=4%2B4%2B7\"
\n" ); document.write( "\"y=15\"
\n" ); document.write( "The line also intersects the parabola at this point, so then,
\n" ); document.write( "\"6%282%29%2Bb=15\"
\n" ); document.write( "\"b=3\"
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