The thing you need to remember is that 25% means 0.25 .
That's the whole problem. The rest is easy.
0.25 x 860 = 215
Answer is in development.
F'(x)=-2x{e^(-x²)}
Equating f'(x)=0,
i.e,
-2x{e^(-x²)}=0....eqn(i)
For maximum slope:
Differentiating (i) wrt x,we get,
4x² {e^(-x²)}-2 {e^(-x²)}=0
{e^(-x²)} [4x²-2]=0
4x²-2=0
x=1/√2
If f(x)=y then f'(x)=dy/dx=slope
So,
Maximum slope
= f'(x)
= -2x{e^(-x²)}
=-2×(1/✓2){e^(-1/✓2)²}
= -✓2{e^(-1/2)}
=(-sqrt 2/sqrt e)
=-sqrt(2/e)➡c is correct
