If (p(x)=5x-4) and (q(x)=2x+7), what is (3p(x)-4q(x))?
Answer and explanation
Correct answer: \(7x-40\)
\(3p(x)-4q(x)=3(5x-4)-4(2x+7)\). Expanding gives \(15x-12-8x-28=7x-40\), so \(7x-40\) is correct. \(7x+16\) results from failing to apply the negative sign to both terms of \(4(2x+7)\). Exam tip: when a minus sign precedes brackets, change the sign of every term inside them.
Frequently asked questions
What is the correct answer to this question?
\(7x-40\)
Why is this the correct answer?
\(3p(x)-4q(x)=3(5x-4)-4(2x+7)\). Expanding gives \(15x-12-8x-28=7x-40\), so \(7x-40\) is correct. \(7x+16\) results from failing to apply the negative sign to both terms of \(4(2x+7)\). Exam tip: when a minus sign precedes brackets, change the sign of every term inside them.
Which subject and chapter does this question cover?
This is a Class 9 Mathematics question. Chapter: Introduction to Polynomials. Topic: Linear polynomials.
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