If y=tan−1(4x1+5x2)+tan−1(2+3x3−2x) then dydx at x=15 is
1.5
2.5
1
10
y = tan−1(5x−x1+5x×x) +tan−1( 23+x1−23×x)
dydx=51+25x2⇒at x=15,dydx=52