Find the y-intercept of the parabola y = x2 + 3x.

The y-intercept is where the parabola crosses the y-axis. The y-intercept is expressed as a coordinate pair, where x is always equal to 0 because the y-axis exists where x=0.

There are 2 ways to find the y-intercept of a function. The first way is to plug in 0 for x because you know that x=0 at the y-intercept. Then, solve for y.

First, plug-in 0 for x

[tex]y=0^2+3(0)[/tex]

Then, simplify the equation

y=0

Since y=0, the y-value of the intercept is 0. Thus making the y-intercept (0,0).

The second, and easier, way to find the y-intercept is to use logic. Since you are plugging in 0 for x, all terms that have variables will equal 0. This means that all that is left are the constants. So, the easiest way to find the y-intercept is to just simplify the constants. Whatever this equals will be the y-value of the y-intercept. Since there are no constants written in this equation, the constant must be 0. If 0 is the constant, then that must mean that the y-value of the intercept is 0.