Advanced MathEasyAdding expressions with three variables
Advanced Math practice question
Which expression is equivalent to (3a + 2b − c) + (a − 5b + 4c)?
- A. 4a − 3b + 3cCorrect
- B. 4a + 7b + 3c
- C. 4a − 3b − 3c
- D. 3a − 3b + 3c
Answer: A. 4a − 3b + 3c
Combine like terms: 3a + a = 4a; 2b − 5b = −3b; −c + 4c = 3c. Result: 4a − 3b + 3c.
Why the other answers are wrong
- B. 4a + 7b + 3c
- 2b − 5b is −3b, not +7b; the signs of the b terms were ignored.
- C. 4a − 3b − 3c
- −c + 4c is +3c: adding 4c to −c goes up, not down.
- D. 3a − 3b + 3c
- 3a + a is 4a; the lone 'a' in the second expression was dropped.
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