An algebra problem by vedit kumawat

Algebra Level pending

Find the sum of all possible solutions of x x that satisfying the equation x ( x k ) = k + 1 x(x-k) = k+1 .

k k 0 0 k + 1 k+1 k 1 k-1 1 1

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2 solutions

x ( x k ) = k + 1 \Rightarrow x(x-k)=k+1

x 2 k x k + 1 = 0 x^2-kx-k+1=0

x 2 k ( x + 1 ) + 1 = 0 x^2-k(x+1)+1=0

Using Vieta's Formula.

Sum of roots = k \boxed{k}

Vedit Kumawat
Jul 16, 2016

Any quadratic equations in x with two roots a and b can be expressed as, (x - a)(x - b) = 0. Which on expansion takes the form, x² - (a + b)x - ab = 0

Hence, the sum of the roots = -(coefficient of x in the expanded form)

Now, x(x - k) = k + 1 => x² - kx - (k + 1) = 0

Hence, sum of the roots = -(-k) = k

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