If #f(x) = 3x^2 -5x#, how do you find and use it to find an equation of the tangent line at the point (2, 2)? I have no idea how to approach this.?

2 Answers
Apr 12, 2015

What is it you are asked to find and use?

Apr 12, 2015

(I'm assuming the "and use it to find" was redundant)

If #f(x) = 3x^2-5x#

Then the derivative (which gives the slope of the tangent) is
#f'(x) =6x-5#

(using #y# in place of #f(x)# for simplicity)

The slope of the tangent at #(x_1,y_1) = (2,2)#
is
#m=6(2)-5 = 7# (substituting #2# for #x# in the expression for #f'(x)#

The slope-point form of an equation for the line is
#(y-y_1) = m(x-x_1)#

or, in this case
#(y-2) = 7(x-2)#
which simplifies as
#y = 7x -12#