Question

Помогите пожалуйста с 1ым пунктом!!!

Answer 1

x^4 - 9x^2 + 20 = 0
x^2 = a ; a > 0
a^2 - 9a + 20 = 0
D = 81 - 80 = 1 = 1^2 
a1 = ( 9 + 1 ) : 2 = 5 
a2 = ( 9 - 1 ) : 2 = 4 
x^2 = 5 
x1 = √ 5 
x2 = - √ 5 
x^2 = 4 
x3 = 2 
x4 = - 2 

Answer 2

x^4 -9x+20=0
x^2=t
t^2-9x+20=0
D=(-9) ^2-4•20=81-80=1 , D>0
t=9+1/2=10/2=5
t=9-1/2=8/2=4
x1=√5, x2= -2, x3=-√5 x4=2

2) x^2=t
t^2-11x+18=0
D= (-11) ^2-4•18=121-72=49, D>0
t= 11+7/2=18/2=9
t=11-7/2=4/2=2
x1=-3, x2=√2, x3=3, x4=-√2