Can b be equal to 15?

Question

If the equation $$x^8 – 3abx + a^2 = 0$$ has one root that is $\ge 3$. And if $a\geq 0$ .

Can $b$ be equal to 15?

I took One root of this equation is (3 + t), where t ≥ 0 And put the value of this root in equation.

Thanks in advance.

@Brian M. Scott Actually it is a multiple choice question. I know the answer is cannot be equal to 15.Thats why i have made up my question according to that.There are 4 more options.

Henry · Accepted Answer · 2012-03-13 08:41:53Z

up vote 2 down vote accepted

Hint: Try to solve for $a$ in terms of $x$ when $b=15$

Your solution should include a square root. Can you spot anything about this square root when $x \ge 3$?

answered Mar 13 '12 at 8:41

Henry
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