u/GraniteGrape

Lets say i have the equation:

y=5x^2+10x+3

I want to calculate slope at a specific point, im wondering why method 1 is invalid.

Method 1: put it into y=mx+b form

y = (5x+10)x+3

now m=5x+10: it is a variable slope based on x location as expected, but the coefficient is wrong

Method 2: derivative

y'=10x+10

now m=10x+10: this is the correct answer I believe

Any help for me to understand this fundamentally woukd be much appreciated!