A coefficient is a number in front of a variable. For example, in the
expression x2-10x+25,
the coefficient
of the x2 is 1 and the coefficient of the x is -10. The third
term, 25, is called a constant.
If the expression were -x2+10x+25,
the coefficient of the x2 would be -1, and the coefficient of
the x would be 10.