NECO 2002 Mathematics · Question 4

Simplify 2a2 -4ab - 6a2 - 10ab + 5ab - 5a2

Options

A.-9(a + b)
B.9(a + b)
C.-9a (a + b)
D.9a(a - b)
E.9b(a + b)

Answer: C. -9a (a + b)

Explanation written with AI and checked against the answer key

Analyze the question: We need to collect like terms. The expression is written as "2a2" which means 2a² (the squared terms), and the "ab" terms are separate. Expression: 2a² − 4ab − 6a² − 10ab + 5ab − 5a² Step 1: Group the a² terms 2a² − 6a² − 5a² = −9a² Step 2: Group the ab terms −4ab − 10ab + 5ab = −9ab Step 3: Combine −9a² − 9ab Step 4: Factorise Take out −9a: −9a(a + b) Check: −9a × a = −9a², and −9a × b = −9ab ✓ Tip: In simplification questions, first group like terms (a² with a², ab with ab), then look for a common factor. Always check by expanding your factorised answer. Also, options A and B have no "a" factor, so they cannot give an a² term, which helps you eliminate them quickly.

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