Решите пожалуйста по алгебре номер 285

1) (15-5)/(3-5^1/2)= 5*(3-5^1/2)/(3-5^1/2)=5;
2) 12/5*5/(4+11^1/2)= 12/5*(16-11)/(4+11^1/2)=
12/5(4-11^1/2)(4+11^1/2)/(4+11^1/2)= 2,4*(4-11^1/2);
3) 1/2*8/(18^1/2-10^1/2)= 1/2*(18-10)/(18^1/2-10^1/2)= 1/2(18^1/2-10^1/2)(18^1/2+10^1/2)/(18^1/2-10^1/2)= 0,5*(3*2^1/2+10^1/2);
4) (50-49)/(50^1/2+7)= (50^1/2-7)(50^1/2+7)/(50^1/2+7)= 5*2^1/2-7;
5) (5^1/2-3^1/2)/(5^1/2+3^1/2)*(5^1/2-3^1/2)/(5^1/2-3^1/2)= (5^1/2-3^1/2)^2/(5-3)= (5-2*5^1/2*3^1/2+3)/2= (8-2*15^1/2)/2= 4-15^1/2;
6) (28^1/2+5^1/2)/(28^1/2-5^1/2)*(28^1/2+5^1/2)/(28^1/2+5^1/2)= (28^1/2+5^1/2)^2/(28-5)=
(28+2*28^1/2*5^1/2+5)/23= (33+4*35^1/2)/23;
7) 2*7/(27^1/2-20^1/2)= 2*(27-20)/(27^1/2-20^1/2)= 2*(27^1/2-20^1/2)(27^1/2+20^1/2)/(27^1/2-20^1/2)= 2*(3*3^1/2+2*5^1/2)= 6*3^1/2+4*5^1/2;
8) (48-45)/(48^1/2-45^1/2)= (48^1/2-45^1/2)(48^1/2+45^1/2)/(48^1/2-45^1/2)= 4*3^1/2+3*5^1/2;
9) -5/26*(-26)/(28^1/2-54^1/2)= -5/26*(28-54)/(28^1/2-54^1/2)= -5/26*(28^1/2-54^1/2)(28^1/2+54^1/2)/(28^1/2-54^1/2)= -5/26(2*7^1/2+3*6^1/2);