Question: if a - b = 3 and a ( power 2 ) + b ( power 2 ) = 21 , find the value of ab .
A) 5
B) 8
C) 4
D) 6
E) 3
Correct answer: D
Grade: 7 | Topic: Expressions and Equations | Difficulty: Easy | Standard: 7.EE.A.1