X varies as one over y. We are accustomed to reading in one dimension from left to right but something like Xn k1. And with the third payment more than one of those numbers could change.
Theres n in two places and also O which the author tells us is the area of your.
Z -a could be read as z plus PAUSE paren negative a close paren. The expression should be x25x-7. I wrote some tips on learning math formulas here. A x - y could be read as a parenthesis x minus y close parenthesis a b2 could be read as a times the square of b Use pauses to audibly group sections of an expression together.