Final answer:
The equation 10x^8 - 6x^4 - 20 can be expressed in quadratic form as 10(x^4)^2 - 6(x^2)^2 - 20 by setting t = x^4 and rewriting it as 10t^2 - 6t - 20 = 0.
Step-by-step explanation:
To express the equation 10x^8 - 6x^4 - 20 in quadratic form, we look for an expression of the form at^2 + bt + c = 0. In our case, we can substitute x^4 for t, transforming our original equation into the form 10t^2 - 6t - 20 = 0. This substitution would yield the answer (a) 10(x^4)^2 - 6(x^2)^2 - 20, which is already in quadratic form with respect to t = x^4. Thus, using the quadratic formula, we can solve for t and then substitute back to solve for x.