Question

If X= 2+√5 then x^3+3x^2-29x is​

Answer 1

Answer:

x= 2+√5

:-) x-2=√5

squaring both sides

(x-2)^2= 5

x^2 +4-4x=5

x^2-4x-1=0,,,,,,,equation 1

dividing x^3+3x^2-29x by equation 1

x^3+3x^2 - 29x/ x^2-4x-1= 0

so the answer is 0

Answer 2

Answer: 7

Step-by-step explanation:

If X= 2+√5

then x^3+3x^2-29x  will be :

(2+√5)^3 + 3*(2+√5)^2 - 29*(2+√5)

=2^3+ (√5)^3+3*2*(√5)*(2+√5) + 3*{ 2^2+2*2*(√5)+(√5)^2 } -58-29√5

=8 +5√5 + 30 + 12√5 + 3*( 9+4√5 ) -58-29√5

= ( 8+30+27-58) + ( 5√5 +12√5 +12√5 -29√5  )

= 7+0

= 7 {Ans}

Formulas: (a+b)^3 = a^3 +b^3 +3ab(a+b)

                 (a+b)^2 = a^2 +2ab +b^2