Which rule represents linear decay and also has initial value 72?
Answer and explanation
Correct answer: y = 72 - 9x
For a rule to show linear decay, it must be linear and have a negative coefficient of x. Its initial value is found by substituting x=0. In option A, y=72-9x, y(0)=72 and the slope is -9, so the value falls by 9 for every unit increase in x. Option B increases, option C starts at 9, and option D is quadratic.
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What is the correct answer to this question?
y = 72 - 9x
Why is this the correct answer?
For a rule to show linear decay, it must be linear and have a negative coefficient of x. Its initial value is found by substituting x=0. In option A, y=72-9x, y(0)=72 and the slope is -9, so the value falls by 9 for every unit increase in x. Option B increases, option C starts at 9, and option D is quadratic.
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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