When you square (-3x²), you need to distribute the exponent of 2 to both the -3 and the x²:
(-3x²)² = (-3)²(x²)²= 9(x⁴)= 9x⁴
So, (-3x²)² = 9x⁴.
When you square (-3x²), you need to distribute the exponent of 2 to both the -3 and the x²:
(-3x²)² = (-3)²(x²)²
= 9(x⁴)
= 9x⁴
So, (-3x²)² = 9x⁴.