Question

Jalil and Victoria are each asked to solve the equation ax – c = bx + d for x. Jalil says it is not possible to isolate x because each x has a different unknown coefficient. Victoria believes there is a solution, and shows Jalil her work:

ax – c = bx + d
ax – bx = d + c
x (a – b) = d + c
x = x equals StartFraction d plus c Over a minus b EndFraction.
How can Victoria justify Step 3 of her work?

Rewrite the expression on the left using the distributive property.
Multiply both sides by x.
Rewrite the expression on the left using subtraction.
Divide both sides by x.

Answer 1

Rewrite the expression on the left using the distributive property.

Explanation: ax − bx = x(a − b) because x is a common factor (factoring via the distributive property). (Note: after this you can divide by a − b only if a ≠ b.)