Q. Factor the following expression completely.x4−8x3+7x2−9x2+72x−63Answer:
Combine Like Terms: First, let's combine like terms in the expression.x4−8x3+(7x2−9x2)+72x−63x4−8x3−2x2+72x−63
Factor by Grouping: Next, we look for common factors in pairs of terms or try to factor by grouping.Grouping the first three terms and the last two terms separately:(x4−8x3−2x2)+(72x−63)
Factor Common Factors: Factor out the greatest common factor from each group. x2(x2−8x−2)+9(8x−7)
Re-evaluate Quadratic: Now, we look for common factors again or try to factor the quadratic.The quadratic x2−8x−2 does not factor nicely, and there are no common factors between the two groups.So, we check if we made a mistake in grouping or factoring.
Correct Mistake: Upon re-evaluating the expression, we realize that the quadratic x2−8x−2 was incorrectly factored. We need to find two numbers that multiply to −2 and add up to −8. However, there are no such integers, and the quadratic is not factorable over the integers. We must have made a mistake in the previous steps.
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