Which rule is linear decay and also has initial value (150)?
Answer and explanation
Correct answer: \(y=150-12x\)
A linear rule has the form \(y=a+bx\), where the initial value is \(a\), found by putting \(x=0\). In \(y=150-12x\), the initial value is 150 and the coefficient of \(x\) is \(-12\), so the value decreases linearly. \(y=12-150x\) also represents decay, but its initial value is 12. Exam tip: put \(x=0\) to check the initial value, and look for a negative slope to identify decay.
Frequently asked questions
What is the correct answer to this question?
\(y=150-12x\)
Why is this the correct answer?
A linear rule has the form \(y=a+bx\), where the initial value is \(a\), found by putting \(x=0\). In \(y=150-12x\), the initial value is 150 and the coefficient of \(x\) is \(-12\), so the value decreases linearly. \(y=12-150x\) also represents decay, but its initial value is 12. Exam tip: put \(x=0\) to check the initial value, and look for a negative slope to identify 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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