The equation that belongs to the quadratic function family is:
y = 2(x + 1.5)² - 55
This equation is in the form \( y = a(x - h)^2 + k \), which is the standard form of a quadratic function where \( a \) is a coefficient, and \( (h, k) \) is the vertex of the parabola.
The other equations do not fit this form:
- \( y = 1.2(2)^x - 8 \) is an exponential function.
- \( y = 7.2x - 15 \) is a linear function.
- \( y = 7(x + 3.5)^{1/2} \) involves a square root, which does not represent a quadratic function.
Thus, the correct answer is the first equation.