Answer:
C
Step-by-step explanation:
To write the quadratic in standard form, make one side equal to 0 using inverse operations. We use inverse operations to move terms on one side to the other.
[tex]x^2-6x-7=3x+2\\\\Subtract 3x\\x^2-6x-3x-7=3x-3x+2\\\\Subtract 2\\x^2-9x-7-2=2-2\\\\x^2-9x-9=0[/tex]