A.12

Mathematics

1 answer:

MrRa [10]3 years ago

3 0

30 because 5 columns and 5 rows that equals to 25 then add 4 blocks on top of the square that will be equal to 29 then add 1 to the corner that will be 30

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What is the quotient? 2 1/2÷(−1 3/4)

anastassius [24]

Answer:

$2 \times \frac{1}{2} \div ( - \frac{13}{4}) = \frac{5}{2} \times - \frac{4}{3} = - \frac{10}{13}$

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3 years ago

When an electric current passes through two resistors with resistance r1 and r2, connected in parallel, the combined resistance,

kondaur [170]

Answer:

The combined resistance of a circuit consisting of two resistors in parallel is given by:

$\frac{1}{R}=\frac{1}{r_1}+\frac{1}{r_2}$

where

R is the combined resistance

$r_1, r_2$ are the two resistors

We can re-write the expression as follows:

$\frac{1}{R}=\frac{r_1+r_2}{r_1r_2}$

$R=\frac{r_1 r_2}{r_1+r_2}$

In order to see if the function is increasing in r1, we calculate the derivative with respect to r1: if the derivative if > 0, then the function is increasing.

The derivative of R with respect to r1 is:

$\frac{dR}{dr_1}=\frac{r_2(r_1+r_2)-1(r_1r_2)}{(r_1+r_2)^2}=\frac{r_2^2}{(r_1+r_2)^2}$

We notice that the derivative is a fraction of two squared terms: therefore, both factors are positive, so the derivative is always positive, and this means that R is an increasing function of r1.

To solve this part, we use again the expression for R written in part a:

$R=\frac{r_1 r_2}{r_1+r_2}$

We start by noticing that there is a limit on the allowed values for r1: in fact, r1 must be strictly positive,

$r_1>0$