Final answer:
Quadratic functions are identified by the highest power of the variable being 2. Functions such as x = 3y^2 – 6y + 5, y + 3 = –2 x^2 + 5, y = 2 x^2 – 8 x + 6, and y = 5 x(x + 9) – 8 are quadratic functions.
Step-by-step explanation:
To identify quadratic functions, we look for equations where the highest power of the variable is 2. Quadratic functions are in the form ax2 + bx + c, where a, b, and c are constants and a is not zero.
x = 3y2 – 6y + 5 is a quadratic function in terms of y.
y + 3 = –2 x2 + 5 is a quadratic function in terms of x.
y = 2 x2 – 8 x + 6 is a quadratic function in terms of x.
y = –7 x – 4 is not a quadratic function as it is linear.
y – 3 x = 4 x3 – x2 + 9 is not a quadratic function as the highest power of x is 3.
y = 5 x(x + 9) – 8 is a quadratic function after expanding and yielding a term with x2.
y – 2 x2 = 3 x – 2 x2 + 4 simplifies to y = 3x + 4, which is linear and therefore not a quadratic function.
The equations that are quadratic functions are:
x = 3y2 – 6y + 5
y + 3 = –2 x2 + 5
y = 2 x2 – 8 x + 6
y = 5 x(x + 9) – 8