Polynomials and fractions

1003032506

Level: 
C
In a parallel circuit the total resistance \( R \) of three components with the resistances \( R_1 \), \( R_2 \), \( R_3 \) is given by the formula \( \frac1R=\frac1{R_1}+\frac1{R_2}+\frac1{R_3} \). Express \( R_1 \) from this formula.
\( R_1=\frac{RR_2R_3}{R_2R_3-R(R_2+R_3)} \)
\( R_1=\frac{R-R_2-R_3}{RR_2R_3} \)
\( R_1=R-\frac{R_2R_3}{R_2+R_3} \)
\( R_1=\frac{R_2R_3-R(R_2+R_3)}{RR_2R_3} \)

1003032507

Level: 
C
Express \( v_1 \) from the formula \( v=\frac{v_1v_2(d_1+d_2 )}{d_1v_2+d_2v_1} \).
\( v_1=\frac{vd_1 v_2}{v_2d_1+v_2d_2-vd_2} \)
\( v_1=\frac{vv_2 d_1}{vd_2-v_2d_1-v_2d_2} \)
\( v_1=\frac{vv_2(d_1+d_2)}{d_1v_2+d_2 v} \)
\( v_1=\frac{v(d_1v_2+d_2 v_1 )}{v_2 (d_1+d_2 )} \)

2010000805

Level: 
C
In a parallel circuit the total resistance \( R \) of three components with the resistances \( R_1 \), \( R_2 \), \( R_3 \) is given by the formula \( \frac1R=\frac1{R_1}+\frac1{R_2}+\frac1{R_3} \). Express \( R_2 \) from this formula.
\( R_2=\frac{RR_1R_3}{R_1R_3-R(R_1+R_3)} \)
\( R_2=\frac{R-R_1-R_3}{RR_1R_3} \)
\( R_2=R-\frac{R_1R_3}{R_1+R_3} \)
\( R_2=\frac{R_1R_3-R(R_1+R_3)}{RR_1R_3} \)