document.write( "Question 747753: Stuck on question 3 which is about equation of the tangent!
\n" ); document.write( "Curve c has equation y=2x^2+6x+7. The ponit p, whose co-ordinates is -1,lies on the curve c. Find the equation of the tangent to C at P.
\n" ); document.write( "Explained answer as i dont get this type of question. \n" ); document.write( "
Algebra.Com's Answer #455105 by Cromlix(4381)\"\" \"About 
You can put this solution on YOUR website!
The point P's coordinate -1 is the x coordinate.
\n" ); document.write( "Assuming it is, substitute -1 into the equation
\n" ); document.write( "y = 2x^2 + 6x + 7 to find the 'y' value.
\n" ); document.write( "y = 2(-1)^2 + 6(-1) + 7
\n" ); document.write( "y = 2 + (-6) + 7
\n" ); document.write( "y = 3 So P's coords are (-1, 3)\r
\n" ); document.write( "\n" ); document.write( "Next differentiate 2x^2 + 6x + 7
\n" ); document.write( " dy/dx = 4x + 6
\n" ); document.write( "Substitute x = -1 into the differentiated equation
\n" ); document.write( " = 4(-1) + 6 = 2 This is the gradient(m)
\n" ); document.write( "at point P.\r
\n" ); document.write( "\n" ); document.write( " Using y - b = m(x - a)
\n" ); document.write( "Substitute P's x and y coords (x = a and y = b)\r
\n" ); document.write( "\n" ); document.write( " y - 3 = 2(x + 1)
\n" ); document.write( " y - 3 = 2x + 2
\n" ); document.write( " y = 2x + 2 + 3
\n" ); document.write( " y = 2x + 5 This is the equation of the tangent at P
\n" ); document.write( "Hope this helps
\n" ); document.write( " \n" ); document.write( "
\n" );