See page 17 and 18 of http://admission.universityofcalifornia.edu/counselors/files/quick-reference-2018.pdf for math validation for fulfilling subject requirements for UC admission purposes.
If you earned a D in second semester algebra 1, a C or higher grade in algebra 2, precalculus, trigonometry, statistics, or calculus will validate it.
If you earned a D in second semester geometry, a C or higher grade in precalculus, trigonometry, or calculus will validate it.
Note: geometry does not validate algebra 1, algebra 2 does not validate geometry unless trigonometry is included, and missing geometry (as opposed to D or F in geometry) cannot be validated.
However, D grades earned in 10th-11th grade are still counted in your GPA for UC frosh admission purposes, unless replaced by repeating the same course.