X^3 - 3x^2 + 5x - 15 = 0 what real value of x is a solution to the above equation?

It is often difficult to factor a polynomial, but notice that the ratio of the coefficient of the first term to that of the second term is 1:3, and that the ratio of the coefficient of the third term to that of the fourth is also 1:3. Therefore, we can factor this cubic by grouping.



We have three solutions in all.

Two imaginary:
 

One real:

60°. A triangle is 180° and that triangle is an isosceles triangle so you take 180-60 which is 120 and divide by 2. The remaining 2 angles are 60°