-4x2 + 28=0

To solve the quadratic equation \(-4x^2 + 28 = 0\), you can follow these steps:

1. Rearrange the equation: \[-4x^2 + 28 = 0\] can be rearranged to isolate the \(x^2\) term: \[-4x^2 = -28\]

2. Divide both sides by -4: \[x^2 = \frac{-28}{-4}\] \[x^2 = 7\]

3. Take the square root of both sides: \[x = \pm \sqrt{7}\]

Thus, the solutions are: \[ x = \sqrt{7} \quad \text{and} \quad x = -\sqrt{7} \]