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x-3-8x-2-7-factorise-it-




Question Number 26638 by shiv15031973@gmail.com last updated on 27/Dec/17
x^3 −8x^2 +7  factorise it.
$$\mathrm{x}^{\mathrm{3}} −\mathrm{8x}^{\mathrm{2}} +\mathrm{7}\:\:\mathrm{factorise}\:\mathrm{it}. \\ $$
Answered by prakash jain last updated on 27/Dec/17
x^3 −8x^2 +7  =x^3 −x^2 −7x^2 +7  =x^2 (x−1)−7(x^2 −1)  =x^2 (x−1)−7(x−1)(x+1)  =(x−1)(x^2 −7x−7)
$${x}^{\mathrm{3}} −\mathrm{8}{x}^{\mathrm{2}} +\mathrm{7} \\ $$$$={x}^{\mathrm{3}} −{x}^{\mathrm{2}} −\mathrm{7}{x}^{\mathrm{2}} +\mathrm{7} \\ $$$$={x}^{\mathrm{2}} \left({x}−\mathrm{1}\right)−\mathrm{7}\left({x}^{\mathrm{2}} −\mathrm{1}\right) \\ $$$$={x}^{\mathrm{2}} \left({x}−\mathrm{1}\right)−\mathrm{7}\left({x}−\mathrm{1}\right)\left({x}+\mathrm{1}\right) \\ $$$$=\left({x}−\mathrm{1}\right)\left({x}^{\mathrm{2}} −\mathrm{7}{x}−\mathrm{7}\right) \\ $$
Commented by kaivan.ahmadi last updated on 27/Dec/17
so good
$$\mathrm{so}\:\mathrm{good} \\ $$

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