Answer:
C
Step-by-step explanation:
Subtraction Property
10x - 30 = 7x
Subtract 7x from both sides.
3x - 30 = 0
3
-6 x 3 = -9
a² + b²
(a + b)² - 2ab ← expand parenthesis using FOIL
= a² + 2ab + b² - 2ab ← collect like terms
= a² + b²