Question

16a4 - 40.a2 + 9 = 0

Answer 1

Oi 

16a^4 - 40a^2 + 9 = 0

x = a^2

16x^2 - 40x + 9 = 0

delta
d^2 = 1600 - 4*16*9 = 1024
d = 32

x1 = (40 + 32)/32 = 72/32 = 9/4
x2 = (40 - 32)/32 = 8/32 = 1/4

a1 = 3/2,  a2 = -3/2
a3 = 1/2, a4 = -1/2

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