When you have an expression to the power of (1/2) that means the same thing as having a square root.
Lets call a=x
To get rid of the square root we square both sides getting:
2x^2+5x+2= 3^2
Simplifying this we get: 2x^2+5x+2=9
We can subtract 9 from both sides getting: 2x^2+5x-7
Now when we solve for this we can use the quadratic formula:
(-b +/- sqrt(b^2-4ac)) / 2a
a=2 , b=5 , c=-7
Plugging in we end up with : (-5 +/- sqrt(81)) /4
This simplifies to : (-5 +/- 9) / 4 ..... (-5+ (-9))/4 OR (-5-(-9))/4
we have x= -14/4 , 1