Question

Find and explain the error in the​ student’s work below.

​Solve: ​ 2m² - 7m​ - 30​ = 0
​ 2m² + 5m​ - 12m​ - 30​ = 0
​ m(2m +​ 5) -​ 6(2m +​ 5) = 0
​ (2m +​ 5)(m -​ 6) = 0
The student states that the answers are 2m​ + 5 and m​ - 6.

Answer 1

The solution set is {-5/2, 6).

Explanation:

2m + 5 and m - 6 are the factors of the function not the solution ( zeroes).

These are equated to 0 to find the zeroes:

2m + 5 = 0 so m = -5/2

and m - 6 = 0 so m = 6.