Question

For f(x) = x2 -4 and g(x) = 2x + 3, what is the domain of f - g?

A) (-90, ∞0)
B) (-2, 2)
C) (2, ∞)
D) [0, %)

Answer 1

To determine the domain of f - g, we need to first find the expression for f - g.

f - g = (x^2 - 4) - (2x + 3)

f - g = x^2 - 2x - 7

The domain of f - g is the set of all real numbers for which the expression x^2 - 2x - 7 is defined.

We know that a quadratic expression of the form ax^2 + bx + c is defined for all real numbers x, so long as the expression under the square root in the quadratic formula (b^2 - 4ac) is non-negative.

In this case, a = 1, b = -2, and c = -7, so the expression under the square root is:

b^2 - 4ac = (-2)^2 - 4(1)(-7) = 4 + 28 = 32

Since 32 is positive, we know that the expression x^2 - 2x - 7 is defined for all real numbers x, and therefore the domain of f - g is all real numbers.

So the answer is not among the choices given.