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Question
- $x^4 - 12x^2 + 36$
- $w^4 - 14w^2 - 32$
- $k^3 + 7k^2 - 44k$
- $2a^3 + 28a^2 + 96a$
- $-x^3 + 4x^2 + 21x$
- $m^6 - 7m^4 - 18m^2$
- $9y^6 + 6y^4 + y^2$
- $8c^4 + 10c^2 - 3$
- $x^3 - 7x^2 + x - 7$
- $4r^3 - 3r^2 - 4r + 3$
- $3p^3 + 5p^2 - 12p - 20$
- $15n^3 - 6n^2 - 25n + 10$
Let's solve problem 14: \(x^4 - 12x^2 + 36\)
Step 1: Recognize as quadratic in \(x^2\)
Let \(u = x^2\), then the expression becomes \(u^2 - 12u + 36\).
Step 2: Factor the quadratic
We need two numbers that multiply to \(36\) and add to \(-12\). Those numbers are \(-6\) and \(-6\). So, \(u^2 - 12u + 36=(u - 6)^2\).
Step 3: Substitute back \(u = x^2\)
\((x^2 - 6)^2\). We can also factor \(x^2 - 6\) as a difference of squares: \(x^2 - 6=(x - \sqrt{6})(x + \sqrt{6})\), so the fully factored form is \(((x - \sqrt{6})(x + \sqrt{6}))^2=(x - \sqrt{6})^2(x + \sqrt{6})^2\), but if we consider integer coefficients only, \((x^2 - 6)^2\) is also acceptable.
Step 1: Let \(u = w^2\)
The expression becomes \(u^2 - 14u - 32\).
Step 2: Factor the quadratic
We need two numbers that multiply to \(-32\) and add to \(-14\). The numbers are \(-16\) and \(2\). So, \(u^2 - 14u - 32=(u - 16)(u + 2)\).
Step 3: Substitute back \(u = w^2\)
\((w^2 - 16)(w^2 + 2)\). Factor \(w^2 - 16\) as a difference of squares: \(w^2 - 16=(w - 4)(w + 4)\). So the fully factored form is \((w - 4)(w + 4)(w^2 + 2)\).
Step 1: Factor out the GCF
The greatest common factor of \(k^3\), \(7k^2\), and \(-44k\) is \(k\). So, \(k(k^2 + 7k - 44)\).
Step 2: Factor the quadratic \(k^2 + 7k - 44\)
We need two numbers that multiply to \(-44\) and add to \(7\). The numbers are \(11\) and \(-4\). So, \(k^2 + 7k - 44=(k + 11)(k - 4)\).
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\((x^2 - 6)^2\) (or \((x - \sqrt{6})^2(x + \sqrt{6})^2\))
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Problem 15: \(w^4 - 14w^2 - 32\)