Solve the equation x^6 + 26x^3 − 27 = 0

While this equation may look complicated, it's actually much easier than it looks - this equation is called a hidden quadratic. This is because it can be rewritten and solved the same way you would solve a quadratic. This becomes clear when you compare it to how a quadratic looks: a w^2 + b w + c. Since the power of the first term is double the power of the second term and the last term is a constant, it can be identified as a hidden quadratic and using the substitution w = x^3, can be rewritten as one (this will be an equation in terms of w).This can be done as follows: x^6 + 26x^3 -27 = 0 (=>) w^2 + 26w -27 = 0 (=>) (w+27) (w-1) = 0 Here is where we substitute x^3 back in to get the equation in terms of x again! (=>) (x^3+27)(x^3-1) = 0 (=>) x^3 = -27 and x^3 = 1 By cube rooting -27 and 1, we get the solutions x=-3 and x =1

SP

Related Maths A Level answers

All answers ▸

integrate e^x sin x dx


(M1) What direction does friction act in? What are the friction equations both generally and in limiting equilibrium? What does it mean for a system to be in equilibrium?


Find the stable points of the following function, determine wether or not they are maxima or minima. y= 5x^3 +9x^2 +3x +2


Given that y = (1 + 3x^2)^(1/3) , use the chain rule to find dy/dx in terms of x.