Test
Rational expressions
Dynamic domain, simplification, operations and evaluation tasks with rational expressions.
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Question 7out of 10
First recognise a difference of squares in the numerator:
x2 − a2 = (x − a)(x + a).
After substituting this product, the numerators and denominators contain matching factors. Cancel x − b and x + a. The remaining factor is the final answer.
Even after the factors are cancelled, the restrictions from the original expression remain: its denominators cannot equal zero.
Question 8out of 10
Replace division by a fraction with multiplication by its reciprocal:
A/B ÷ C/D = A/B · D/C.
Then factor the difference of squares:
x2 − a2 = (x − a)(x + a).
Cancel matching factors. Remember that the divisor cannot equal zero, so in addition to denominator restrictions you must exclude the value that makes the numerator of the second fraction zero.
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Sample questions
- State the restriction for 1/(x − (___)).
- Simplify (x² − ___²)/(x − ___), where x ≠ ___.
- Add a/x and b/x when a = ___, b = ___.
- Simplify ((x2 − ___)/(x − ___)) · ((x − ___)/(x + ___)), where x ≠ ___ and x ≠ −___.
- Simplify ((x2 − ___)/(x − ___)) ÷ ((x − ___)/(x − ___)), where x ≠ ___ and x ≠ ___.
Rational expressions
A rational expression contains fractions involving polynomials. Its domain is restricted by denominators: no denominator may equal zero. Record excluded values before simplifying.
Operations with rational expressions
For multiplication, factor numerators and denominators and cancel common factors. For addition or subtraction, find a common denominator. Only factors may be cancelled, not separate terms in a sum; retain all restrictions from the original expression in the final result.
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