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Home › Forums › Math › Using the quadratic formula to solve x^2 + 20 = 2x, what are the values of x?
Tagged: quadratic formula
(A) 1 – i √19 and 1 + i √19
(B) -1 – i √19 and 1 + i √19
(C) 1 – i √21 and 1 + i √21
(D) -1 – i √21 and 1 + i √21
The correct answer is (A) :
Given : x^2 + 20 = 2x
Then : x^2 – 2x + 20 = 0
a = 1, b = -2, c = 20
The quadratic formula is :
x = (- b ± √(b^2 – 4ac)) / (2a)
Substitute the values in formula
x = -(-2) ± √((-2)^2 – 4(1)(20)) / 2(1)
x = 2 ± 2 i √19 / 2
x = 1 – i √19 and 1 + i √19
Hence the value of X is x = 1 – i √19 and 1 + i √19