因为x^2+3x-5=0
所以x^2(x^2 + 3x - 5) = 0,即x^4 + 3x^3 - 5x^2 = 0 ---(1)
同理有3x(x^2 + 3x - 5) = 0,即3x^3 + 9x^2 - 15x = 0 ---(2)
(1)式-(2)式消去三次项,得:
x^4 - 14x^2 + 15x = 0 --- (3)
因为x^2 + 3x - 5 = 0
所以10x^2 + 30x - 50 = 0 ---(4)
(3)式+(4)式,得:
x^4 - 4x^2 + 45x - 50 = 0
故
x^4 - 4x^2 + 45x + 3 = 53
希望有用.