An introduction to mathematics, by A. N. Whitehead.

66 INTRODUCTION TO MATHEMATICS
representing some definite number other than
zero, such as 1 or 2 in the examples above,
are written on the left-hand side, so that the
whole left-hand side is equated to the number
zero. The first man to do this is said to
have been Thomas Harriot, born at Oxford
in 1560 and died in 1621. But what is the
importance of this simple symbolic procedure? It made possible the growth of the
modern conception of algebraic form.
This is an idea to which we shall have continually to recur; it is not going too far to
say that no part of modern mathematics can
be properly understood without constant recurrence to it. The conception of form is
so general that it is difficult to characterize
it in abstract terms. At this stage we shall
do better merely to consider examples. Thus
the equations 2x-3 =0, x-1=0, 5x-6 = 0,
are all equations of the same form, namely,
equations involving one unknown x, which is
not multiplied by itself, so that x2, x3, etc., do
not appear. Again 3x2 - x +1 = 0, x2 = 3x +2
=0, x2-4=0, are all equations of the same
form, namely, equations involving one unknown x in which x Xx, that is x2, appears.
These equations are called quadratic equations. Similarly cubic equations, in which
x3 appears, yield another form, and so on.
Among the three quadratic equations given
above there is a minor difference between the