Factorise 3(x-2y)² - 2(x-2y)-8
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Plz I need correct answer with full explanation my tutor told me that here I have to take let K is (x-2y) but do I have to do lile the numbers which are outside the bracket like in asending or descending order of powers like 2k²-2k-8,can we write this one like 8-2k-2k²...
heyyyy buddies plz help me.
And thank you so much mathdude for your answer with full explanation
Answers & Comments
Verified answer
Answer:
[tex]\boxed{\bf\:3 {(x - 2y)}^{2} - 2(x - 2y) - 8 =\left(x - 2y - 2\right)\left(3x - 6y + 4\right) \: } \\ [/tex]
Step-by-step explanation:
Given algebraic expression is
[tex] \sf \: 3 {(x - 2y)}^{2} - 2(x - 2y) - 8 \\ [/tex]
Let assume that x - 2y = k
So, above expression can be rewritten as
[tex] \sf \: = \: 3 {k}^{2} - 2k - 8 \\ [/tex]
[tex] \sf \: = \: 3 {k}^{2} - 6k + 4k - 8 \\ [/tex]
[tex] \sf \: = \: 3k(k - 2) + 4(k - 2) \\ [/tex]
[tex] \sf \: = \: (k - 2)(3k + 4) \\ [/tex]
On substituting the value of k, we get
[tex] \sf \: = \: \left[x - 2y - 2\right]\left[3(x - 2y) + 4\right] \\ [/tex]
[tex] \sf \: = \: \left(x - 2y - 2\right)\left(3x - 6y + 4\right)\\ [/tex]
Hence,
[tex]\implies\boxed{\bf\:3 {(x - 2y)}^{2} - 2(x - 2y) - 8 =\left(x - 2y - 2\right)\left(3x - 6y + 4\right) \: } \\ [/tex]
[tex]\rule{190pt}{2pt}[/tex]
Alternative Method with ascending powers of x
Given algebraic expression is
[tex] \sf \: 3 {(x - 2y)}^{2} - 2(x - 2y) - 8 \\ [/tex]
Let assume that x - 2y = k
So, above expression can be rewritten as
[tex] \sf \: = \: 3 {k}^{2} - 2k - 8 \\ [/tex]
[tex] \sf \: = \: - 8 - 2k + 3 {k}^{2} \\ [/tex]
[tex] \sf \: = \: - 8 + 4k - 6k + 3{k}^{2} \\ [/tex]
[tex] \sf \: = \: 4(- 2 + k) + 3k(- 2+ k) \\ [/tex]
[tex] \sf \: = \: (- 2 + k)(4 + 3k) \\ [/tex]
[tex] \sf \: = \: (k - 2)(3k + 4) \\ [/tex]
On substituting the value of k, we get
[tex] \sf \: = \: \left[x - 2y - 2\right]\left[3(x - 2y) + 4\right] \\ [/tex]
[tex] \sf \: = \: \left(x - 2y - 2\right)\left(3x - 6y + 4\right)\\ [/tex]
Hence,
[tex]\implies\boxed{\bf\:3 {(x - 2y)}^{2} - 2(x - 2y) - 8 =\left(x - 2y - 2\right)\left(3x - 6y + 4\right) \: } \\ [/tex]
[tex]\rule{190pt}{2pt}[/tex]
Additional Information:
[tex]\begin{gathered}\: \: \: \: \: \: \begin{gathered}\begin{gathered} \footnotesize{\boxed{ \begin{array}{cc} \small\underline{\frak{\pmb{{More \: identities}}}} \\ \\ \bigstar \: \bf{ {(x + y)}^{2} = {x}^{2} + 2xy + {y}^{2} }\:\\ \\ \bigstar \: \bf{ {(x - y)}^{2} = {x}^{2} - 2xy + {y}^{2} }\:\\ \\ \bigstar \: \bf{ {x}^{2} - {y}^{2} = (x + y)(x - y)}\:\\ \\ \bigstar \: \bf{ {(x + y)}^{2} - {(x - y)}^{2} = 4xy}\:\\ \\ \bigstar \: \bf{ {(x + y)}^{2} + {(x - y)}^{2} = 2( {x}^{2} + {y}^{2})}\:\\ \\ \bigstar \: \bf{ {(x + y)}^{3} = {x}^{3} + {y}^{3} + 3xy(x + y)}\:\\ \\ \bigstar \: \bf{ {(x - y)}^{3} = {x}^{3} - {y}^{3} - 3xy(x - y) }\:\\ \\ \bigstar \: \bf{ {x}^{3} + {y}^{3} = (x + y)( {x}^{2} - xy + {y}^{2} )}\: \end{array} }}\end{gathered}\end{gathered}\end{gathered}[/tex]