In the line y = -x + 15, what are the slope and y-intercept?
Answer and explanation
Correct answer: Slope -1, y-intercept 15
Use the governing slope-intercept form y = mx + c. In this form, the coefficient m of x is the slope, while the constant c is the y-intercept. In y = -x + 15, the coefficient of x is -1, so the slope is -1. The constant term is 15, meaning the graph meets the y-axis at the point (0, 15); hence the y-intercept is 15. Thus option B is correct. Option A swaps the roles of the coefficient and constant, option C loses the negative sign, and option D assigns incorrect values and signs. A quick check is that increasing x by 1 changes y by -1, confirming the slope, while putting x = 0 gives y = 15, confirming the intercept.
Frequently asked questions
What is the correct answer to this question?
Slope -1, y-intercept 15
Why is this the correct answer?
Use the governing slope-intercept form y = mx + c. In this form, the coefficient m of x is the slope, while the constant c is the y-intercept. In y = -x + 15, the coefficient of x is -1, so the slope is -1. The constant term is 15, meaning the graph meets the y-axis at the point (0, 15); hence the y-intercept is 15. Thus option B is correct. Option A swaps the roles of the coefficient and constant, option C loses the negative sign, and option D assigns incorrect values and signs. A quick check is that increasing x by 1 changes y by -1, confirming the slope, while putting x = 0 gives y = 15, confirming the intercept.
Which subject and chapter does this question cover?
This is a Class 9 Mathematics question. Chapter: Introduction to Polynomials. Topic: Slope and y-intercept.
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