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Please i really need help with it to finish my hw. it would greatly appreciated. ty

2006-11-13 10:35:18 · 2 answers · asked by Hopeicouldhelp 4 in Education & Reference Homework Help

2 answers

The domain is the set of all values the variables can have so that the value of the expression is defined. A rational expression has a definite value as long as the denominator is not zero, since division by zero is undefined. So any set of values for the variables is in the domain just as long as that set doesn't make the denominator of the expression equal zero.

Example : (x^2 + 5xy + 4) / (x - 3)(y + 7) is a rational expression. You can calculate its value for any values of x and y you plug into it just as long as the denominator (x - 3)(y + 7) doesn't equal zero. But (x - 3)(y + 7) = 0 if x = 3 or y = -7. So any pair (x,y) is in the domain of the original expression unless x = 3 or y = -7.
(1,2), (5,10), (-100,100), (4/3, -1/2) are all in the domain.
(2,-7), (3,41), (-8,-7), (3,-7) are not in the domain.

2006-11-13 11:04:23 · answer #1 · answered by wild_turkey_willie 5 · 0 0

The domain is the all X values that can be put into an equation. For your standard line and parabola (X+2 orX^2) the domain goes from negative infinity to postive inf (infinity). For something like square root of X its all positive numbers because there you can't take the square root of negative number. A big rule is to look for discontinuities or places where the graph isn't complete. Like (x+2)/(X+5) you can't divide by zero so -5 can't be an answer. Look for these sign and you'll do fine.

2006-11-13 11:11:29 · answer #2 · answered by asmidsk@verizon.net 3 · 0 0

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