Question

If one root of the equation x²-4x-12=0 is 6,

find the other root

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Answer 1

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x²−4x+k=0

has two roots:

√2±4−k

if one of them is 6 than

2±√4−k = 6∣−2

±√4−k=4∣y²

4−k=16∣−4

−k=12∣÷−1

k=−12

Also note the other root is −2:

x²−4x−12=(x−6)(x+2)