describe when it is and when it is not necessary to use a common denominator when adding, subtracting, multiplying, and dividing rational expressions.

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Step-by-step explanation:

For multiplication and division, the denominator of the result is developed as part of the algorithm for performing these operations on rational expressions. For example, ...

  (a/b)(c/d) = (ac)/(bd)

  (a/b)/(c/d) = (ad)/(bc)

It is not necessary to make the operands of these operations have a common denominator before the operations are performed. That being said, in some cases, the division operation can be simplified if the operands do have a common denominator or a common numerator:

  (a/b)/(c/b) = a/c

  (a/b)/(a/c) = c/b

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If the result of addition or subtraction is to be expressed using a single denominator, then the operands must have a common denominator before they can be combined. That denominator can be developed "on the fly" using a suitable formula for the sum or difference, but it is required, nonetheless.

  (a/b) ± (c/d) = (ad ± bc)/(bd)

This formula is equivalent to converting each operand to a common denominator prior to addition/subtraction:

Note that the denominator 'bd' in this case will not be the "least common denominator" if 'b' and 'd' have common factors. Even use of the "least common denominator" is no guarantee that the resulting rational expression will not have factors common to the numerator and denominator.

For example, ...

  5/6 - 1/3 = 5/6 -2/6 = 3/6 = 1/2

The least common denominator is 6, but the difference 3/6 can still be reduced to lower terms.

If we were to use the above difference formula, we would get ...

  5/6 -1/3 = (15 -6)/18 = 9/18 = 1/2

the system of inequity is

step-by-step explanation:

from the given graph it is noticed that we have two related lines. one is solid and another is dashed.

if a line passing through two points, then the equation of line is

the solid line passing through the points (0,4) and (4,0).

the related equation of solid line is .

similarly, find the related equation of dashed line. the dashed liune passing through the points (0,0) and (3,1).

the related equation of dashed line is

from the given graph it is noticed that the point (0,1) lies on the shaded region, therefore the point (0,1) must be satisfied by the related equations.

check the related equations by the point (0,1).

this statement is true if the sign of inequality is < instead of equality. since it is an solid line therefore the sign of inequality will be . the required inequality is

similarly, check the second related equation.

it is a dashed line, so this statement is true if the sign of inequality is > . the required inequality is