If $20x^{2} — 30x + 1 = 0$, then what is the value of $25x^{2}+\frac{1}{16x^{2}}$
Answer & explanation
Correct answer: option 2
If $K+\frac{1}{K}=n$
then, $K^2+\frac{1}{K^2}$ = n2 – 2 × k × \(\frac{1}{k}\)
If $20x^{2} — 30x + 1 = 0$,
then what is the value of $25x^{2}+\frac{1}{16x^{2}}$
Divide $20x^{2} — 30x + 1 = 0$ by 5x on both sides to get the desired format of the equation,
5x + \(\frac{1}{4x^2}\) = \(\frac{30}{4}\) = \(\frac{15}{2}\)
So, $25x^{2}+\frac{1}{16x^{2}}$ = ( \(\frac{15}{2}\) )2 – 2 × 5x × \(\frac{1}{4x}\)
$25x^{2}+\frac{1}{16x^{2}}$ = \(\frac{225}{4}\) - \(\frac{5}{2}\)
$25x^{2}+\frac{1}{16x^{2}}$ = \(\frac{225 - 10}{4}\) = \(\frac{215}{4}\)
$25x^{2}+\frac{1}{16x^{2}}$ = 53$\frac{3}{4}$