Want to calculate Apsl?

Mu1 = fpb Apsl (d-dn1)

Where

Mu1 = 56.6*106

fpb = 0.95*1750

d = 156.7

dn = fpb Apsl / 0.9 fcu b

fcu = 50

b = 1168

Mu1 = 56.6*106 = ( 0.95*1750* Apsl*156.7 ) – (0.95*1750* Apsl)^2 / 0.9*50*1168

The values I have worked out are not appropriate to the solution I am trying to solve. I the areas of the equation where I don’t understand is moving 156.7 & ^2

If anybody could help I would be grateful