What substitution should be used to rewrite 4x^4 -21x^2+20=0 as a quadratic equation

u = x²

Step-by-step explanation:

4x⁴ − 21x² + 20 = 0

4(x²)² − 21x² + 20 = 0

If we substitute u = x²:

4u² − 21u + 20 = 0

for this pair of functions g(x)=x-2 and f(x)=|x| is (g o f)(a)= |a| -2

step-by-step explanation:

g(x)=x-2

f(x)=|x|

(g o f)(a)=?

(g o f)(x)=g(f(x))

(g o f)(x)=g(|x|)

(g o f)(x)=|x|-2

(g o f)(a)=|a|-2

68719476736

step-by-step explanation:

8*8*8*8*8*8*8*8*8*8*8*8=68719476736