Determine the real roots of each equation
(5x^2+20)(3x^2-48) = 0
(x^2+1)(2x^2 - x - 13) = 0
Possible typo in the first question? As it stands there are no real roots.
If, as I suspect, you mean $\displaystyle (5x^2+20)(3x^2-48)=0$. In this case ignore the first bracket.
Divide through by 3 and ignore the first brackets: $\displaystyle x^2-16=0$
This is a classic example using the difference of two squares.
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With the second one you can also ignore the first bracket as it has no real solutions