Question 168381
Find the value(s)that can replace the variable in the expression and cause the expression to be undefined. 
(2x-3)/(2x^2 +5x-3)

= (2x-3)/[(2x^2 -1)(x + 3)]

The denominator cannot be zero.
If 2x^2-1=0, x = +/-sqrt(1/2)
If x+3 = 0, x = -3
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Ans: x cannot be +/-sqrt(1/2) or -3
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and 
(2x+4)/(x^2 + 4)

No Real Number value of x will make the denominator zero.
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Cheers,
Stan H.