-7(2a2-4) Multiply
I assume you mean:
-7(2a^2-4) = -14a^2 + 28
If you can do -7(3-4) you should have no trouble with this. Use the same steps.
To multiply -7 by (2a^2-4), you need to distribute -7 to each term inside the parentheses.
Step 1: Distribute -7 to 2a^2
-7 * 2a^2 = -14a^2
Step 2: Distribute -7 to -4
-7 * -4 = 28
Putting it all together, the result of -7(2a^2-4) is -14a^2 + 28.