2х^2+5х^2-7=0

To solve the quadratic equation \(2x^2 + 5x^2 - 7 = 0\), first combine like terms:

\[ (2 + 5)x^2 - 7 = 0 \]

\[ 7x^2 - 7 = 0 \]

Next, add \(7\) to both sides:

\[ 7x^2 = 7 \]

Now, divide both sides by \(7\):

\[ x^2 = 1 \]

Taking the square root of both sides gives:

\[ x = \pm 1 \]

Thus, the solutions to the equation \(2x^2 + 5x^2 - 7 = 0\) are:

\[ x = 1 \quad \text{and} \quad x = -1 \]