Question

rewrite the following equation as a function of x.
21x + 3y - 45 = 0
a. f(x) = -7x - 6
b. f(x) = 3x + 6
c. f(x) = -7x + 15
d. f(x) = 7x - 15

Explanation:

Step1: Isolate the term with y

Start with the equation \(21x + 3y - 45 = 0\). Add 45 to both sides and subtract \(21x\) from both sides to get \(3y=-21x + 45\).

Step2: Solve for y (or f(x))

Divide every term by 3: \(y=\frac{-21x + 45}{3}\). Simplify each term: \(\frac{-21x}{3}+\frac{45}{3}=-7x + 15\). So \(f(x)=-7x + 15\).

Answer:

C. \(f(x)=-7x + 15\)