<span>this is pretty hard but here is your answer
</span>
y = x^2 - 10x + 25 - 25
<span> y = (x-5)^2 - 25 </span>
<span> y+25 = (x-5)^2 </span>
<span> x-5 = +/-sqrt(y+25) </span>
<span> And you get TWO
inverses: </span>
<span> x = 5 + sqrt(y+25),
for x>=5 </span>
<span> x = 5 - sqrt(y+25),
for x<=5</span>
0.813 is your answer because 7 is higher than 5 which means you have to round it up and not down