Question

If x^2 + ax + 10 = 0 and x^2 + bx - 10 = 0 have a common root, then a^2 - b^2 is equal to :
(A) 10
(B) 20
(C) 30
(D) 40​

Answer 1

Answer:

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Answer 2

Answer:

Simply think that what are the factors of 10 = 1,2,5,10 so we took 2 and 5 two factors and put the value of a = 7 and we put value of b = 3 because the value is negative so, 5-2 = 3 and after that put the value of a and b to the formula a^2 - b^2 = (a+b)(a-b) → a^2 - b^2 = (7+3)(7-3) → 10×4 = 40

So answer is D.