Question

resolva as equações, sendo U=R a) x⁴+4x²-21=0

Answer 1

$x^{4} + 4 x^{2} -21=0 y² +4y -21=0$

a=1  b=4  c=-21
Δ=4²- 4(1)(-21)
Δ=16 + 84
Δ= 100

y= -4 (+-) √100$\frac{-4 (+-) √100}{2}$
y1= $\frac{4+10}{2}$=7
y2= $\frac{4-10}{2}$=-3

y=x²         y=x²
7=x²        -3=x²
x=√7        x=√3