Math Problem Statement

The graph of linear function k passes through the points (−7, 0) and (1, 8) .

Which statement must be true? A.The zero of k is 7 .
B.The graph of k passes through the point (−1, −8) .
C.The x-intercept of the graph of k is −7 . D.The slope of the graph of k is −43 .

Solution

We are given that the graph of the linear function kk passes through the points (7,0)(-7, 0) and (1,8)(1, 8).

Step 1: Check the x-intercept

The x-intercept is the point where the function crosses the x-axis, meaning the y-coordinate is 0. Since the point (7,0)(-7, 0) is given, this is the x-intercept. Thus:

  • C: The x-intercept of the graph of k is 7-7 must be true.

Step 2: Find the slope

The slope mm of a line passing through two points (x1,y1)(x_1, y_1) and (x2,y2)(x_2, y_2) is calculated by the formula:

m=y2y1x2x1m = \frac{y_2 - y_1}{x_2 - x_1}

Using the points (7,0)(-7, 0) and (1,8)(1, 8):

m=801(7)=81+7=88=1m = \frac{8 - 0}{1 - (-7)} = \frac{8}{1 + 7} = \frac{8}{8} = 1

So, the slope is 1, not 43-43, which means D is false.

Step 3: Evaluate other options

  • A: The zero of kk is 7 is false because the zero (x-intercept) is already determined to be 7-7, not 7.
  • B: The graph of kk passes through the point (1,8)(-1, -8) is false. With a slope of 1 and passing through the x-intercept at (7,0)(-7, 0), we can calculate the equation of the line to verify this.

Step 4: Write the equation of the line

Using the point-slope form of a line yy1=m(xx1)y - y_1 = m(x - x_1), where m=1m = 1 and a point on the line is (7,0)(-7, 0):

y0=1(x(7))    y=x+7y - 0 = 1(x - (-7)) \implies y = x + 7

Substitute x=1x = -1 to check if the line passes through (1,8)(-1, -8):

y=(1)+7=6y = (-1) + 7 = 6

Since y=6y = 6, not 8-8, B is false.

Conclusion:

The correct statement is C: The x-intercept of the graph of kk is 7-7.

Would you like further details or have any questions?

Here are five related questions:

  1. How is the equation of a line derived from two points?
  2. What is the significance of the slope in a linear function?
  3. How can you determine the y-intercept from two points?
  4. Why is the x-intercept important in understanding the graph of a line?
  5. How would the equation change if the slope was negative?

Tip: To find the slope of a line between two points, always remember the formula y2y1x2x1\frac{y_2 - y_1}{x_2 - x_1}.

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Math Problem Analysis

Mathematical Concepts

Algebra
Linear Equations
Slope-Intercept Form

Formulas

Slope formula: m = (y2 - y1) / (x2 - x1)
Point-slope form: y - y1 = m(x - x1)

Theorems

Slope-Intercept Theorem
Zero of a Function

Suitable Grade Level

Grades 8-10