To write the expression \((x^2 - 4)(x^2 - 9)\) as linear factors, we first factor each quadratic expression.
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The expression \(x^2 - 4\) is a difference of squares, which can be factored as: \[ x^2 - 4 = (x - 2)(x + 2) \]
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The expression \(x^2 - 9\) is also a difference of squares, and can be factored as: \[ x^2 - 9 = (x - 3)(x + 3) \]
Now we can combine these factorizations: \[ (x^2 - 4)(x^2 - 9) = (x - 2)(x + 2)(x - 3)(x + 3) \]
Thus, the expression \((x^2 - 4)(x^2 - 9)\) written as linear factors is: \[ (x - 2)(x + 2)(x - 3)(x + 3) \]