Let I=∫410[x2−28x+196]+[x2][x2]dx
⇒I=∫410[(14−x)2]+[x2][x2]dx...(i)
Use ∫abf(x)dx=∫abf(a+b−x)dx
I=∫410[x2]+[(14−x)2][(14−x)2]dx...(ii)
By adding equations (i)&(\mathrm{ii}), we get
2I=∫410[x2]+[(14−x)2][(14−x)2]+[x2]dx
⇒2I=∫410dx
⇒2I=6
⇒I=3