The function is given as,
y= ∫ 0 a x x + a−x dx (1)
By using the property ∫ 0 b f( x )dx = ∫ 0 b f( b−x )dx it can be written as,
y= ∫ 0 a a−x a−x + a−( a−x ) dx = ∫ 0 a a−x a−x + x dx (2)
By adding the equation (1) and (2), we get,
2y= ∫ 0 a x x + a−x dx + ∫ 0 a a−x a−x + x dx = ∫ 0 a x + a−x x + a−x dx = ∫ 0 a 1dx 2y= [ x ] 0 a
Further simplify the above integral as,
2y=[ a−0 ] y= a 2
Thus, the solution of the integral is a 2 .