12a2 – 3ab + 2b ; a = −5, b = 4

Sure, let's substitute the values of a and b into the expression.

The expression is: 12a^2 - 3ab + 2b

Step 1: Substitute a = -5 and b = 4 into the expression.

= 12(-5)^2 - 3(-5)(4) + 2(4)

Step 2: Simplify the expression.

= 12(25) + 3(5)(4) + 8

= 300 + 60 + 8

Step 3: Add the values.

= 368

So, the value of the expression 12a^2 - 3ab + 2b when a = -5 and b = 4 is 368.