Q. Factor the following expression completely.x4−4x2−7x3+28x+10x2−40Answer:
Rearrange terms in descending order: First, we should rearrange the terms of the polynomial in descending order of the powers of x.x4−7x3+6x2+28x−40
Look for common factors: Next, we look for common factors in groups of terms. We can group the terms as follows: x4−7x3 + 6x2+28x - −40.
Factor by grouping: Factor by grouping. For the first group x4−7x3, we can factor out an x3, and for the second group 6x2+28x, we can factor out a 2x. This gives us:x3(x−7)+2x(3x+14)−40
Find common factor: We notice that the term 40 does not have a common factor with the other groups. However, we can still look for a common factor between the terms x3(x−7) and 2x(3x+14). We see that there is no common factor, so we need to look for a different approach to factor the expression completely.
Try different grouping: Let's try to factor by grouping in a different way. We can rearrange the terms to see if there's a better grouping: x4−7x3+10x2−4x2+28x−40 Now, we group them as follows: (x4−7x3+10x2)+(−4x2+28x−40).
Factor by grouping again: For the first group x4−7x3+10x2, we can factor out an x2, and for the second group −4x2+28x−40, we can factor out a −4. This gives us:x2(x2−7x+10)−4(x2−7x+10)
Factor out common factor: We now have a common factor of (x2−7x+10) in both groups. We can factor this out: (x2−7x+10)(x2−4)
Factor simple trinomial: The quadratic x2−7x+10 can be factored further since it is a simple trinomial. We look for two numbers that multiply to 10 and add up to −7. These numbers are −5 and −2. So we can write:(x−5)(x−2)(x2−4)
Factor difference of squares: The term x2−4 is a difference of squares and can be factored as (x+2)(x−2). So the fully factored form of the expression is:(x−5)(x−2)(x+2)(x−2)
Final fully factored form: We notice that (x−2) is repeated, so we can write it with an exponent:(x−5)(x−2)2(x+2)This is the completely factored form of the expression.
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