Answer:
B
Step-by-step explanation:
Combine like terms. Like terms have same variable with same power.
2x & (-12x) are like terms and
-7x² & 4x² are like terms
A = 2x - 7x² + 3
B = 4x² - 12x
A + B = 2x - 7x² + 3 + 4x² - 12x
= 2x - 12x - 7x² + 4x² + 3
= (2-12)x + (-7 + 4)x² + 3
= -10x + (-3x²) + 3
= -3x² - 10x +3
