$\text{Công thức:}$
$P_{hp}=I^2.R$
$P_{hp}=\dfrac{P^2}{U^2}.R$
$\text{Biến đổi}$
$P_{hp}=I^2.R$
$=>I^2=\dfrac{P_{hp}}{R}$
$=>R=\dfrac{P_{hp}}{I^2}$
$P_{hp}=\dfrac{P^2}{U^2}.R$
$=>R=\dfrac{P_{hp}.U^2}{P^2}$
$=>U^2=\dfrac{R.P^2}{P_{hp}}$
$=>P^2=\dfrac{P_{hp}.U^2}{R}$