Which rule has initial value (90) and decay rate (6)?
Answer and explanation
Correct answer: \(y=90-6x\)
A linear rule has the form \(y=a+mx\), where \(a\) is the initial value and \(m\) is the rate of change. A decay rate of 6 means that the rate is \(-6\). Therefore, the rule with initial value 90 is \(y=90-6x\). In \(y=90+6x\), the value increases rather than decays. Exam tip: check the constant term for the initial value and a negative coefficient of \(x\) for decay.
Frequently asked questions
What is the correct answer to this question?
\(y=90-6x\)
Why is this the correct answer?
A linear rule has the form \(y=a+mx\), where \(a\) is the initial value and \(m\) is the rate of change. A decay rate of 6 means that the rate is \(-6\). Therefore, the rule with initial value 90 is \(y=90-6x\). In \(y=90+6x\), the value increases rather than decays. Exam tip: check the constant term for the initial value and a negative coefficient of \(x\) for decay.
Which subject and chapter does this question cover?
This is a Class 9 Mathematics question. Chapter: Introduction to Polynomials. Topic: Linear growth and decay.
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