A student solved the equation
+2 _ 5x = 2x2
- x - 21 using the
process below. What property justifies the step from line Ill to line IV?
1 0 = x2 + 4x - 21
11 0 = ×2+ 7x - 3x - 21
III 0 = x(x + 7) - 3(x + 7)
IV 0 = (x - 3)(x + 7)
V x = 3 or x = -7
A Substitution
(B) Distributive Property
C) Commutative Property of
Addition
) Associative Property of
Multiplication