Question 107306
Simplify:
{{{R[t] = 1/((1/R[1])+(1/R[2]))}}} Add the fractions in the denominator using the LCD of ({{{R[1]*R[2]}}})
{{{R[t] = 1/((R[1]+R[2])/(R[1]*R[2]))}}} Now divide the numerator (that's the 1) by the denominator.  Remember when you divide by a fraction, you invert the fraction and multiply.
{{{R[t] = (R[1]*R[2])/(R[1]+R[2])}}} This is the the formula for the combined resistance of two resistors connected in parallel.