Finding Domains: y=-(x+7/8)² - 1⅕ Function Analysis

Question

Find the positive and negative domains of the function below:

y=(x+78)2115 y=-\left(x+\frac{7}{8}\right)^2-1\frac{1}{5}

Step-by-Step Solution

The function y=(x+78)2115 y = -\left(x + \frac{7}{8}\right)^2 - 1\frac{1}{5} is represented in vertex form, where the vertex of the parabola is at x=78 x = -\frac{7}{8} , and the maximum value at the vertex is y=115 y = -1\frac{1}{5} . Since the parabola opens downwards due to the negative coefficient of the squared term, its maximum value is also its highest possible value, which is a negative number 115 -1\frac{1}{5} .

Therefore, the function does not reach any positive value for any real number x x ; it only takes on non-positive values. Consequently, the determination of positive and negative domains is as follows:

  • x<0 x < 0 : The function can assume all values since the entire parabola lies below the x-axis, producing a negative range for all x x .
  • x>0 x > 0 : No x x can produce a positive y y value, resulting in no positive values.

Therefore, the positive and negative domains as concluded from this analysis are:

x<0: x < 0 : all x x

x>0: x > 0 : none

Answer

x < 0 : all x x

x > 0 : none