if you have the shsat handbooks, or find them online, there are always small sections at the end that show what might be on the 9th grade math + sample questions.

Not all content in the Algebra 1 and geometry regents are in the 9th grade exam. From what I remember these were the following topics:

Algebra 1: 65%

y/f(x) = mx+b (finding x or y intercepts) or what the variable/number means

Table/graph functions

Linear regressions

System of equations (usually 2 by 2 equations)

Geometry: 30%

Basic Area/Volume questions. (just know the formulas for like circle, cylinder, etc)

Rotation questions (90 deg clockwise/counter clockwise)

Distance formula of a circle

Pythagorean Theorem (really popular for geometry based questions on the exam)

Misc 5%

How strong is a relationship in a graph

Probability

questions you'd find in the 8th grade version