本日のC.A.D.

? tst12([all,all],[a,b,c,d,x,y],eq,"y<(x+a)^15+b,y<(x+c)^15+d");Ans(1);
 *** using Lazard's method (MPP17).
[y,2]
[x,1]
[d,4]
[c,7]
[b]
[a,1]
time = 1min, 36,784 ms.
3 3(0,0) 37(84,7) 535(26,54) 1647(52,12) 9(0,6) 
 *** combined adjacent 8 cells.
1[true,true,c = [a-c,1],d = [b-d,1],true,true]
time = 9,594 ms.
Wolfram Language 12.3.0 Engine for Linux x86 (64-bit)
Copyright 1988-2021 Wolfram Research, Inc.

In[1]:= Reduce[ForAll[{x,y},Equivalent[y<(x+a)^5+b,y<(x+c)^5+d]],{a,b,c,d},Reals,WorkingPrecision->30]//Timing   

Out[1]= {0.104536, c == a && d == a^5 + b - c^5}

In[2]:= Reduce[ForAll[{x,y},Equivalent[y<(x+a)^6+b,y<(x+c)^6+d]],{a,b,c,d},Reals,WorkingPrecision->30]//Timing   

Out[2]= {0.476967, c == a && d == a^6 + b - c^6}

In[3]:= Reduce[ForAll[{x,y},Equivalent[y<(x+a)^7+b,y<(x+c)^7+d]],{a,b,c,d},Reals,WorkingPrecision->30]//Timing   

Out[3]= 
{0.528524, (a < 0 && c == a && d == a^7 + b - c^7) || (a == 0 && c == 0 && d == b) || 
  (a > 0 && c == a && d == a^7 + b - c^7)}

In[4]:= Reduce[ForAll[{x,y},Equivalent[y<(x+a)^8+b,y<(x+c)^8+d]],{a,b,c,d},Reals,WorkingPrecision->30]//Timing   

Out[4]= {36.708199, c == a && d == a^8 + b - c^8}

In[5]:= Reduce[ForAll[{x,y},Equivalent[y<(x+a)^9+b,y<(x+c)^9+d]],{a,b,c,d},Reals,WorkingPrecision->30]//Timing   

Out[5]= {4.41101, c == a && d == a^9 + b - c^9}

In[6]:= Reduce[ForAll[{x,y},Equivalent[y<(x+a)^10+b,y<(x+c)^10+d]],{a,b,c,d},Reals,WorkingPrecision->30]//Timing 

Out[6]= {368.027142, c == a && d == a^10 + b - c^10}

In[7]:= Reduce[ForAll[{x,y},Equivalent[y<(x+a)^11+b,y<(x+c)^11+d]],{a,b,c,d},Reals,WorkingPrecision->30]//Timing 

Reduce::cadpr: The cylindrical algebraic decomposition algorithm used by Reduce
     failed due to a too low WorkingPrecision. Increasing the value of WorkingPrecision may allow the algorithm
     to succeed.
^C
Interrupt> a

Out[7]= $Aborted

In[8]:= Reduce[ForAll[{x,y},Equivalent[y<(x+a)^11+b,y<(x+c)^11+d]],{a,b,c,d},Reals,WorkingPrecision->60]//Timing 

Out[8]= {27.447685, c == a && d == a^11 + b - c^11}