Find Negative Area: Solving y+1=(x+3)² Parabola Problem

Question

Find the negative area of the function

y+1=(x+3)2 y+1=(x+3)^2

Video Solution

Solution Steps

00:00 Find the negative domain of the function
00:03 Use the shortened multiplication formulas and open the brackets
00:08 Arrange the equation so that it remains a function
00:15 Note the coefficient of X squared is positive
00:19 When the coefficient is positive, the function is smiling
00:23 Now we want to find the intersection points with the X-axis
00:27 At the intersection points with the X-axis, Y=0, we'll substitute and solve
00:37 Take the square root
00:43 When taking a square root there are always 2 solutions (positive and negative)
00:50 Solve each possibility to find the points, isolate X
01:04 These are the intersection points with the X-axis
01:09 Let's draw the function according to the intersection points and type of function:
01:22 The function is negative while it's below the X-axis
01:32 And this is the solution to the question

Step-by-Step Solution

To find the negative area of the given parabola, we need to determine where the function y=(x+3)21 y = (x + 3)^2 - 1 is below the x-axis. This corresponds to finding when the parabola is negative.

First, let's set the equation y=(x+3)21 y = (x + 3)^2 - 1 equal to zero and solve for x x to find the roots:

  • Set (x+3)21=0 (x + 3)^2 - 1 = 0 .

  • This simplifies to (x+3)2=1 (x + 3)^2 = 1 .

  • Taking square roots gives x+3=±1 x + 3 = \pm 1 .

  • Thus, x+3=1 x + 3 = 1 gives x=2 x = -2 , and x+3=1 x + 3 = -1 gives x=4 x = -4 .

The roots are x=4 x = -4 and x=2 x = -2 . The parabola opens upwards since the coefficient of x2 x^2 is positive. Therefore, it is negative (below the x-axis) between these roots.

To verify, choose a test point between the roots, say x=3 x = -3 :

  • Plug into the equation: y=((3)+3)21=01=1 y = ((-3) + 3)^2 - 1 = 0 - 1 = -1 , which is negative.

Therefore, the function is negative on the interval -4 < x < -2 .

The correct answer is -4 < x < -2 .

Answer

-4 < x < -2