Question

Verifying a Solution
Consider this equation.

7.8 + 2(0.75m + 0.4) = -6.4m + 4(0.5m - 0.8)


Mia solved the equation and determined that m = 2. Is she correct?
She is incorrect because when substituting 2 for m the result was a true statement.
She is incorrect because when substituting 2 for m the result was a false statement.
She is correct because when substituting 2 for m the result was a true statement.
She is correct because when substituting 2 for m the result was a false statement.

Answer 1

She is incorrect because substituting m = 2 gives a false statement.

Check: left = 7.8 + 2(0.75·2 + 0.4) = 7.8 + 2(1.5 + 0.4) = 7.8 + 3.8 = 11.6
right = -6.4·2 + 4(0.5·2 - 0.8) = -12.8 + 4(1 - 0.8) = -12.8 + 0.8 = -12.0

11.6 ≠ -12.0, so m = 2 is not a solution. (The actual solution is m = -2.)