Hey, i've been doing a maths practice paper for revision but i've come across a question i don't understand. Can anyone help me??

Find the exact roots of the equation 2x(squared)+8x-5=0 giving your answers in their simplest form.

The answer is -2(plus or minus)1/2 (square root) 26

but i just keep getting -2(plus or minus) (square root) 24

:S i don't know where i'm going wrong

Thanks for your help

xx