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Question Number 192390 by TUN last updated on 16/May/23

Give the function:  x^2 −7x−8=0  have two roots x_(1 ) and x_2   No solving the function   Find: x_1 ^3 +x_2 +2023

Givethefunction:x27x8=0havetworootsx1andx2NosolvingthefunctionFind:x13+x2+2023

Answered by deleteduser1 last updated on 17/May/23

x_1 ^3 +x_2 +2023=p; x_2 ^3 +x_1 +2023=q  p+q=(x_1 +x_2 )^3 −3x_1 x_2 (x_1 +x_2 )+x_1 +x_2 +4046  x_1 +x_2 =7;x_1 x_2 =−8⇒p+q=343+168+7+4046=4564  pq=(x_1 x_2 )^3 +x_1 ^4 +2023(x_1 ^3 +x_2 ^3 )+x_2 ^4 +x_1 x_2 +2023(x_2 +x_1 )  +2023^2 =−512+[(7^2 +16)^2 −128]+2023(511)−8+2023(7)  +2023^2 =5144020  p+q=4464;pq=5144020⇒p(4464−p)=5144020  ⇒p=2030,q=2534 (up to symmetry)

x13+x2+2023=p;x23+x1+2023=qp+q=(x1+x2)33x1x2(x1+x2)+x1+x2+4046x1+x2=7;x1x2=8p+q=343+168+7+4046=4564pq=(x1x2)3+x14+2023(x13+x23)+x24+x1x2+2023(x2+x1)+20232=512+[(72+16)2128]+2023(511)8+2023(7)+20232=5144020p+q=4464;pq=5144020p(4464p)=5144020p=2030,q=2534(uptosymmetry)

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