It represents the value of the expression when the variable (t) is zero.
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If this is supposed to be an expression for ballistic motion, the constant could represent the initial height of the object in feet. There is nothing in your problem statement indication what this expression is suppose to represent. It could be pennies of profit for selling t trinkets, for all we know—where the constant term represents some initial balance you have before you sell any.
It can represent many things depending on what context the expression is used in. Most commonly, the constant term represents the y-intercept of the expression when it is graphed e.g. the graph of y = -16t² - 8t + 24 has a y-intercept of 24.
It can also represent the initial value if the expression is used in a word problem context
