To solve general equations in one variable or to find the zeros or roots of a function press the Solve button.
If the function is not constant it solves the equation f(x) = 0 [or r(θ) = 0, in polar case] on a bounded interval. The solution set is the x-intercepts of the Cartesian graph of the function on the bounded interval.
Remark: To solve the equation x2 - 3x + 2 = 0, just type in the left hand side and press Solve.
There are trivial cases that you will find extraneous "roots" or "x-intercepts" appear because of round off error. This can happen when the graph of the function is very close to the x-axis on a sub-interval. For example, the graph of x10 is very close to the x-axis on a sub-interval about 0 which produces "unwanted roots".
It is always helpful to look at the graph when finding the x-intercepts of functions.
To solve a system of linear equations try the Linear System Solver by entering the relevant augmented matrix.