I'm not certain, but I think you have to subtract 5 - (-5) = 5 + 5 = 10 for the function. Then you replace all of the x's in x4+x2 + 5x with 10's. Doing that, we have 104+102+5×(10). 104=10000, 102=100, 5(10) = 50 . Then we have 10000+100+50 which can be easily added together to get the answer.