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Question Number 116578 by bobhans last updated on 05/Oct/20
solve for x     determinant (((1   x    x^2     x^3 )),((1   2    2^2     2^3 )),((1   3    3^2     3^3 )),((1   4    4^2     4^3 )))= 0
solveforx|1xx2x3122223133233144243|=0
Answered by bemath last updated on 05/Oct/20
  determinant (((1      0           0            0)),((1  2−x     4−x^2    8−x^3 )),((1  3−x     9−x^2    27−x^3 )),((1  4−x   16−x^2   64−x^3 )))=0    determinant (((2−x     4−x^2     8−x^3 )),((3−x    9−x^2     27−x^3 )),((4−x   16−x^2    64−x^3 )))= 0  (2−x)(3−x)(4−x)  determinant (((1    2+x   4+2x+x^2 )),((1   3+x    9+3x+x^2 )),((1   4+x   16+4x+x^2 )))= 0  (2−x)(3−x)(4−x){(12+7x)−(16+12x)+(6+5x)} = 0  2(2−x)(3−x)(4−x)=0  → { ((x=2)),((x=3)),((x=4)) :}
|100012x4x28x313x9x227x314x16x264x3|=0|2x4x28x33x9x227x34x16x264x3|=0(2x)(3x)(4x)|12+x4+2x+x213+x9+3x+x214+x16+4x+x2|=0(2x)(3x)(4x){(12+7x)(16+12x)+(6+5x)}=02(2x)(3x)(4x)=0{x=2x=3x=4
Answered by Olaf last updated on 05/Oct/20
det(A) = −2x^3 +18x^2 −52x+48  det(A) = −2(x−2)(x−3)(x−4)  det(A) = 0 ⇔ x = 2 or 3 or 4
det(A)=2x3+18x252x+48det(A)=2(x2)(x3)(x4)det(A)=0x=2or3or4
Answered by 1549442205PVT last updated on 05/Oct/20
A=  determinant (((1   x    x^2     x^3 )),((1   2    2^2     2^3 )),((1   3    3^2     3^3 )),((1   4    4^2     4^3 )))= 0  ⇔A= determinant ((2,4,8),(3,9,(27)),(4,(16),(64)))−x determinant ((1,4,8),(1,9,(27)),(1,(16),(64)))  +x^2  determinant ((1,2,8),(1,3,(27)),(1,4,(64)))−x^3  determinant ((1,2,4),(1,3,9),(1,4,(16)))  =48−52x+18x^2 −2x^3 =0  ⇔x^3 −9x^2 +26x−24=0  ⇔(x−2)(x−3)(x−4)=0  ⇔x∈{2,3,4}
A=|1xx2x3122223133233144243|=0A=|248392741664|x|148192711664|+x2|12813271464|x3|1241391416|=4852x+18x22x3=0x39x2+26x24=0(x2)(x3)(x4)=0x{2,3,4}

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