Solve the equation 8x^6 + 7x^3 -1 = 0
The first thing to recognise is this is a quadratic in disguise, therefore we can rewrite the equation in terms of a new variable y.
Where y=x3
The equation then becomes 8y2+7y-1=0 .
We then factorise this into (8y-1)(y+1)=0 and work out y=1/8 or -1.
Then substitute this into the equation for y=x3 so that x3=1/8 and x3=-1
Solving for x gives us x=1/2 or -1
Things to note: A common mistake is that even though the square root of -1 has no solution the cube root of -1 does.
KP
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