If (y=210-9x), what happens to (y) when (x) increases from (4) to (14)?
Answer and explanation
Correct answer: y decreases by 90
The change in x is 14 - 4 = 10. The coefficient of x is -9, so for every increase of 1 in x, y decreases by 9. Thus, the total change in y is -9 × 10 = -90, meaning y decreases by 90. The value 10 is the change in x, not in y. Exam tip: In a linear equation y = a + bx, multiply b by Δx to find the total change in y.
Frequently asked questions
What is the correct answer to this question?
y decreases by 90
Why is this the correct answer?
The change in x is 14 - 4 = 10. The coefficient of x is -9, so for every increase of 1 in x, y decreases by 9. Thus, the total change in y is -9 × 10 = -90, meaning y decreases by 90. The value 10 is the change in x, not in y. Exam tip: In a linear equation y = a + bx, multiply b by Δx to find the total change in y.
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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