Maximums and minimums
Surely you've passed through a geometry or trigonometry course to get to calculus. Now if you can recall, you probably looked at parabolas, which have a maximum or minimum point, depending on the equation.
Let's say we have this equation. The first thing we have to do is get the derivative, which is 4x-5. Now that we have the derivative, we have to equal it to zero and then isolate x, which will give us x=5/4. Now that we have that, we must substitute it into the original equation, where you'll get the value of y (if you have a variable raised to the square, use the general formula). Now write the value of x on a line and choose 2 values; one bigger and one lower, and substitute them in the derivative. The answers should be alternating: +-+, -+-, if they are the same for example :--+,++- it is wrong. You can now get the decrease and increase of the function. The decrease is from negative infinity to the value of x you got, and increase is from your x value to positive infinity. The inflexion point is your x and y values (x,y).