The curve y2=x is a sideways parabola opening to the right with vertex at the origin (0,0).
The line x=4 is a vertical line.
Since y2=x gives y=+x (upper half) and y=−x (lower half), the parabola is symmetric about the x-axis.
The region runs from x=0 (vertex) to x=4.
Total Area=∫04[x−(−x)]dx
=∫042xdx
=2∫04x1/2dx
=2[3/2x3/2]04
=2×32[x3/2]04
=34[x3/2]04
43/2=(4)3=23=8
=34[8−0]
=34×8
=332 sq. units