Giải các phương trình sau:

a) $\frac{{\left(7-\mathrm{x}\right)}^2}{4}-{\left(\mathrm{x}+5\right)}^2=0;$

b) $4{\mathrm{x}}^2+{\left(\mathrm{x}-1\right)}^2-{\left(2\mathrm{x}+1\right)}^2=0;$ 

c) ${\mathrm{x}}^3+1=\left(\mathrm{x}+1\right)\left(2-\mathrm{x}\right);$

d)  ${\mathrm{x}}^2-4\mathrm{x}-5=0.$