Find Values of x for y=2x²-50 Where y < 0: A Quadratic Exploration

Question

Look at the following function:

y=2x250 y=2x^2-50

Determine for which values of x x the following is true:

f\left(x\right) < 0

Step-by-Step Solution

To solve the inequality 2x^2 - 50 < 0 , we follow these steps:

  • Set the quadratic equation equal to zero to find the roots: 2x250=0 2x^2 - 50 = 0 .

  • Rearrange and solve for x x :

2x250amp;=02x2amp;=50x2amp;=25xamp;=±25xamp;=±5 \begin{aligned} 2x^2 - 50 &amp;= 0\\ 2x^2 &amp;= 50\\ x^2 &amp;= 25\\ x &amp;= \pm \sqrt{25}\\ x &amp;= \pm 5 \end{aligned}

These roots, x=5 x = -5 and x=5 x = 5 , are where the function y=2x250 y = 2x^2 - 50 is equal to zero.

We now examine the intervals determined by these roots to find where the function is negative:

  • x < -5

  • -5 < x < 5

  • x > 5

Since the quadratic is an upward opening parabola (coefficient of x2 x^2 is positive), it attains its minimum value between its roots and increases outside them.

Testing a point in each interval:

  • (For x=0 x = 0 in the interval -5 < x < 5): y = 2(0)^2 - 50 = -50 < 0 .

  • (Other intervals will be positive) such as x=6 x = -6 or x=6 x = 6, will have y > 0 .

Thus, the function is negative in the interval -5 < x < 5 .

Therefore, the values of x x that satisfy 2x^2 - 50 < 0 are:

-5 < x < 5 .

Answer

-5 < x < 5