If the equations x² + bx - a = 0 and x²- ax +b= 0 have atleast one common root, then
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Now here we have two equations with exactly one common root
x^2 + ax + b = 0 and x^2 + bx + a = 0
Let y be the exact common root.
Therefore, y^2 + ay + b = 0 …..(1)
And y^2 + by + a = 0 ……..(2)
Now subtracting eq (1) from (2) we get ,
y(a - b) + (b - a) = 0
y (a - b) = - (b -a)
y (a - b) = (a - b)
y = 1
Therefore the common root is 1.
Substituting value of y in equation (1)
(1)^2 + a(1) + b = 0
1 + a + b = 0
a + b = -1
Therefore value of a + b is -1
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