find an equation of the tangent line at the given point P.
y= 3x^2 + 5x -7, P(-2, -5)
step 1 ... find $\displaystyle y'(x)$
step 2 ... using $\displaystyle y'(x)$, find the value of the slope of the curve at point P, i.e. $\displaystyle y'(-2)$
step 3 ... using the slope found in step 2 and the coordinates of the given point P, use the point-slope form of a linear equation to find the equation of the tangent line.
$\displaystyle \textcolor{red}{y - y_1 = m(x - x_1)}$