Question

hy

plz solv this wid full. steps​

Answer 1

hey mate

here is your answer

1/3-√8

=1(3+√8)/3square - √8square

= 3+√8/9-8

=3+√8/1=3+√8

=x= 3+√8

= x cube - 2 x square - 7 x + 5

(3+√8) cube - 2(3+√8) square -7(3+√8) +5

27+8√8 - 18 - 16 - 21 - 7√8 +5

27 - 18 -16 - 21 + 5 +8√8-7√8

-23+√8

hope it helped you

plz mark as brainiest

Answer 2

Given :

$\mathsf{x=\dfrac{1}{3-\sqrt{8}}}$

$\mathsf{\therefore x=\dfrac{1}{3-\sqrt{8}}}\\\\\implies \mathsf{x=\dfrac{1}{3-\sqrt{8}}\times \dfrac{3+\sqrt{8}}{3+\sqrt{8}}}\\\\\implies \mathsf{x=\dfrac{3+\sqrt{8}}{(3-\sqrt{8})(3+\sqrt{8})}}\\\\\implies \mathsf{x=\dfrac{3+\sqrt{8}}{3^2-(\sqrt{8})^2}}\\\\\implies \mathsf{x=\dfrac{3+\sqrt{8}}{9-8}}\\\\\implies \mathsf{x=3+\sqrt{8}}$

$\boxed{\mathsf{x=3+\sqrt{8}}}$

Required to find :

$\mathsf{x^3-2x^2-7x+5}$

$\mathsf{x^3=(3+\sqrt{8})^3}\\\\\implies \mathsf{3^3+(\sqrt{8})^3+3\times 3\times \sqrt{8}(3+\sqrt{8})}\\\\\implies \mathsf{27+8\sqrt{8}+9\sqrt{8}(3+\sqrt{8})}\\\\\implies \mathsf{27+8\sqrt{8}+27\sqrt{8}+9\times \sqrt{8}\times \sqrt{8}}\\\\\implies \mathsf{27+35\sqrt{8}+72}\\\\\implies \mathsf{99+35\sqrt{8}}$

$\mathsf{-2x^2=-2(3+\sqrt{8})^2}\\\\\implies \mathsf{-2(3^2+(\sqrt{8})^2+2\times 3\times \sqrt{8})}\\\\\implies \mathsf{-2(9+8+6\sqrt{8})}\\\\\implies \mathsf{-2(17+6\sqrt{8})}\\\\\implies \mathsf{-34-12\sqrt{8}}$

$\mathsf{-7x=-7(3+\sqrt{8})}\\\\\implies \mathsf{-21-7\sqrt{8}}$

Adding all the three values with 5 we get :

$\implies \mathsf{99+35\sqrt{8}-34-12\sqrt{8}-21-7\sqrt{8}+5}\\\\\implies \mathsf{(99-34-21+5)+\sqrt{8}(35-12-7)}\\\\\implies \mathsf{99-50+16\sqrt{8}}\\\\\implies \mathsf{49+16\sqrt{8}}\\\\\implies \mathsf{49+32\sqrt{2}}$

$\mathbb{ANSWER}\\\\\boxed{\boxed{\mathtt{49+32\sqrt{2}}}}$

NOTE :-

$\bigstar \mathtt{(a+b)^3=a^3+b^3+3ab(a+b)}\\\\\bigstar \mathtt{(a+b)^2=a^2+b^2+2ab}\\\\\bigstar \mathtt{(a+b)(a-b)=a^2-b^2}$