To simplify rational expressions, first we need to know what they are. They are fractions that have polynomials on both their numerators and denominators.
You just can simplify factors, not terms. That means you have to factorize the nominator and the denominator:
2x2+8x+8 = 6x-2
Now, both are divisible by 2. So just divide them by 2, the result would be: