A recent question to when to use of and when for/to for solution suggested that of appears only in context of chemistry, and the word means something very different then. But I recalled almost universally finding
2are the solutions of the equation
x^2 = 4
I consulted the dictionary and to my surprise I found:
2. Mathematics A value or values which, when substituted for a variable in an equation, make the equation true. For example, the solutions to the equation
x^2 = 4are
I consulted the ngram and it made me even more confused than before.
It seems like solution to the equation is a relatively new trend, but picking up.
So, what's the official stance on correctness of the preposition to go with solution in mathematics?