Select all of the following that are quadratic equations.
5 x2+ 15 x = 0
6x-1= 4x+7
x2.4 x= 4x+7
02x-1=0
3 x2 +5 x - 7 = 0
32x²=1=0

Step-by-step explanation:

5 x2+ 15 x = 0 needs to be retyped as 5x^2 + 15x = 0.  This is a quadratic because the highest x power is 2.

6x-1= 4x+7  lacks x^2 and so is linear, not quadratic.

x2.4 x= 4x+7 Needs to be retyped:  x^2.4 ...   Still not valid.  A quadratic equation may contain only the whole number powers 2, 1 and 0.

02x-1=0   Not quadratic.  02x is improper.

3 x2 +5 x - 7 = 0   Needs retyping:  3x^2 + 5x - 7 = 0 is a quadratic; notice that the highest x power is x^2.

32x²=1=0  Please retype.  1 is never equal to 0 (as was typed here).  However, the term 32x^2 could be part of a quadratic.

2 5/8 is the final answer! : )