Given x 2-3x-5 = 0, find the value of X 3-14x + 5

Given x 2-3x-5 = 0, find the value of X 3-14x + 5

x3-14x+5=x(x2-14x)+5∵x2-3x-5=0,∴x2=3x+5,∴x3-14x+5=x(3x+5-14)+5=x(3x-9)+5=3x2-9x+5=3(3x+5)-9x+5=9x+15-9x+5=20.