clear[x,pnp]​​​​pnp=2564855351​​
clear[x,2564855351]
2564855351
​​​​​​{p1=Plot[((x*Sqrt[pnp^3/(pnp*x^2+x)]+x^4/(pnp^2+x))-pnp),{x,10000,50000}],p2=Plot[pnp-(Sqrt[((x^2*pnp^4+2*pnp*x^5)+x^8)/pnp^4]-(1-x^2/(2*pnp))),{x,10000,50000}]}​​​​Show[p1,p2,ImageSize720]

20000
30000
40000
50000
0.0
0.2
0.4
0.6
0.8
1.0
,
10000
30000
2.56481×
9
10
2.56482×
9
10
2.56483×
9
10
2.56484×
9
10

20000
30000
40000
50000
0.2
0.4
0.6
0.8
1.0
​​​​​​NSolve[((x*Sqrt[pnp^3/(pnp*x^2+x)]+x^4/(pnp^2+x))-pnp)==pnp-(Sqrt[((x^2*pnp^4+2*pnp*x^5)+x^8)/pnp^4]-(1-x^2/(2*pnp)))]
{}