Which rule has initial value (28) and growth of (9) per step?
Answer and explanation
Correct answer: \(y=28+9x\)
A linear rule has the form \(y=a+bx\), where \(a\) is the initial value and \(b\) is the change per step. Here, \(a=28\) and the growth is \(b=9\), so the rule is \(y=28+9x\). In \(y=28-9x\), the value decreases by 9 each step, so it represents decay, not growth. Exam tip: put \(x=0\); the correct rule must give \(y=28\).
Frequently asked questions
What is the correct answer to this question?
\(y=28+9x\)
Why is this the correct answer?
A linear rule has the form \(y=a+bx\), where \(a\) is the initial value and \(b\) is the change per step. Here, \(a=28\) and the growth is \(b=9\), so the rule is \(y=28+9x\). In \(y=28-9x\), the value decreases by 9 each step, so it represents decay, not growth. Exam tip: put \(x=0\); the correct rule must give \(y=28\).
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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