y=(x^15+2*x^6)^20
y'=(20*(x^15+2*x^6)^19)*(x^15+2*x^6)'= (20*(x^15+2*x^6)^19)*(15*x^14+12*x^5)==15*(x^14)*20*(x^15+2*x^6)^19+12*(x^5)*20*(x^15+2*x^6)^19 = 300*(x^14)*(x^15+2*x^6)^19 +240*(x^5)* (x^15+2*x^6)^19
