2x(x-1)-x^2 (x+2)+x^3-x+4=0 4x(3x+2)-6x(2x+5)+21(x-1)=0

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1. ` a) ` ` 2x(x – 1) – x^{2}(x + 2) + x^{3} – x + 4 = 0 `

   ` => 2x^{2} – 2x – x^{3} – 2x^{2} + x^{3} – x + 4 = 0 `

   ` => -x^{3} + x^{3} + 2x^{2} – 2x^{2} – 2x – x + 4 = 0 `

   ` => -3x + 4 = 0 `

   ` => -3x = -4 `

   ` => x = 4/3 `

   ` b) ` ` 4x(3x + 2) – 6x(2x + 5) + 21(x – 1) = 0 `

   ` => 12x^{2} + 8x – 12x^{2} – 30x + 21x – 21 = 0 `

   ` => 12x^{2} – 12x^{2} + 8x – 30x + 21x – 21 = 0 `

   ` => -x – 21 = 0 `

   ` => -x = 21 `

   ` => x = -21 `

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