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If 2x 2 + 6x = 36, what are the possible values of x ?
Correct IncorrectThe correct answer is (B).
Getting to the Answer: There is a common factor of 2 in all of the terms, so divide them all by that factor: 2x 2 ⁄2 + 6x ⁄2 = 36 ⁄2. This simplifies to x 2 +3x=18. Subtract 18 from both sides to get x 2 +3x-18=0. Using reverse FOIL, find two factors of -18 that sum to 3. These are 6 and -3, so the equation factors to (x+6)(x-3)=0. The values that make the factors equal to 0 are -6 and 3.
(A) Incorrect: these are the solutions to x 2 +9x-36=0
(B) Correct: this matches the correct calculation
(C) Incorrect: this reverses the signs of the solutions
(D) Incorrect: these are the solutions to x 2 -9x-36=0
(E) Incorrect: these are the solutions to x 2 -27x+180=0