Without the use of the solve function of a calculator how do I solve the equation: #x^4-5x^3-x^2+11x-30=0#?
Given that #(x-5)# and #(x+2)# are factors of #f(x)#
Given that
2 Answers
The zeros are
Explanation:
We are told that
#x^4-5x^3-x^2+11x-30 = (x-5)(x^3-x+6)#
We are told that
#x^3-x+6 = (x+2)(x^2-2x+3)#
The discriminant of the remaining quadratic factor is negative, but we can still use the quadratic formula to find the Complex roots:
#x^2-2x+3# is in the form#ax^2+bx+c# with#a=1# ,#b=-2# and#c=3# .
The roots are given by the quadratic formula:
#x = (-b+-sqrt(b^2-4ac))/(2a)#
#= (2+-sqrt((-2)^2-(4*1*3)))/(2*1)#
#= (2+-sqrt(4-12))/2#
#= (2+-sqrt(-8))/2#
#= (2+-sqrt(8)i)/2#
#= (2+-2sqrt(2)i)/2#
#=1+-sqrt(2)i#
Let us try without knowing that
The constant term equals the roots product,so
This coefficient is an integer value whose factors are
We can represent the polynomial as
Calculating the right side and comparing both sides we obtain
Solving for
Evaluating the roots of