問2題數學題!!

1. 2c - d/c² d + c+d/cd²
=2c - 2d/c² d² + 2c+d/c²d²
=2c - 2d+ 2c+d / c² d²
=4c - d / c² d²

2. L=a+(n-1)d find n
L= a+(n-1)d
L - a= (n - 1)d
L - a = dn - d
L - a+ d = dn
L - a+ d / d = n
n = L - a+ d / d

2) L = a+dn-d
dn=L+d-a
n=(L+d-a)/d [ans]

1.3c-(c+d)c² d
2.n=L-n+1