Tangent=y+10x−5=0
Normal=x−10y+50=0.
The equation of the curve is y=x4−bx3+13x2−10x+5.
∴dydx=4x3−3bx2+26x−10
⇒(dydx)(0,5)=−10
The equation of tangent at (0,5) is
y−5=(dydx)(0,5)(x−0)
⇒y−5=−10(x−0)
⇒10x+y−5=0
The equation of the normal at (0,5) is
y−5=−1(dydx)(0,5)(x−0)
⇒y−5=110(x−0)
⇒x−10y+50=0.