Question

1. ​​Use what you have learned to find the solutions of the polynomial equation shown below.

Answer 1

If (x^2 -10) is one of the factors, that can be further factored into:
(x - sqrt(10) ) * (x+sqrt(10)) =0
making 2 of the 4 solutions equal:
3.1623 and -3.1623

I then used an algebraic long division calculator
http://calculus-calculator.com/longdivision/
to calculate:
x^4 + 5x^3 ‒ x^2 ‒ 50x ‒ 90 divided by x^2 -10 which equals

x^2 + 5x + 9

Using the quadratic formula, the roots of that equation are:
x = -5 + sqrt (-11) / 2
and
x = -5 - sqrt (-11) / 2

Both of those roots are not real.

I tried using online graphing calculators for x^4+5x^3-x^2-50x-90=0 but none worked.

2.  For this equation,
3x^2 ‒ 8x + k = 0
I used my OWN quadratic formula calculator
http://www.1728.org/quadratc.htm
and found that real roots no longer exist after "k" is greater than 5.3