If (p(x)=rx-6) and (p(4)=18), what is the value of (p(-2))?
Answer and explanation
Correct answer: -18
Given \(p(x)=rx-6\) and \(p(4)=18\), we have \(4r-6=18\). Thus \(4r=24\), so \(r=6\). Now \(p(-2)=6(-2)-6=-12-6=-18\). Therefore, \(-18\) is the correct answer. Getting \(-12\) is a common error caused by forgetting the constant term \(-6\). Exam tip: first use the given function value to find the coefficient, then substitute the required input.
Frequently asked questions
What is the correct answer to this question?
-18
Why is this the correct answer?
Given \(p(x)=rx-6\) and \(p(4)=18\), we have \(4r-6=18\). Thus \(4r=24\), so \(r=6\). Now \(p(-2)=6(-2)-6=-12-6=-18\). Therefore, \(-18\) is the correct answer. Getting \(-12\) is a common error caused by forgetting the constant term \(-6\). Exam tip: first use the given function value to find the coefficient, then substitute the required input.
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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