Answer:
Correct answer is m = -3
Step-by-step explanation:
First you must to multiply two binomials:
(mx + 8) (2x - 4) = 2mx² - 4mx + 16x - 32 = 2mx² + (16 - 4m) x - 32
After that you equalize this expression and given expression
- 6x² + 28x - 32 = 2mx² + (16 - 4m) x - 32
After that you equalize the coefficients with the same monomials:
-6 = 2m and 28 = 16 - 4m
m = -6/2 = - 3 and check in another
28 = 16 - 4 (-3) => 28 = 16 + 12 = 28 => 28 = 28 identity is correct
God with you!!!