Question

Which equation is a quadratic equation?
3x − y = 8x + 2
y = 7x(5 − 2x) + 9
7x2 + y = (3 + x)(7x − 1)
y − 3 = (x2 − 3)(8x + 3)

Answer 1

the one so that when expanded yields a
ax^2+bx+c=y form

Answer 2

A isnt
becaus subtracting 3x from both sides doesn't yield any x^2 term.
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D isn't because if you expand right hand side you get a 8x^3 term making it a cupic not a quadratic


only leaves b and c and they kinda weird

Answer 3

b and c seem to both be quadratic

Answer 4

B for sure is so i'd go with b

Answer 5

however if in doubt then lets expand C
7x2 + y = (3 + x)(7x − 1)

y=(3 + x)(7x − 1)-7x^2
^ ^ I can already tell we are going to have a 7x^2 term. And it will cancel with the -7x^2 term so it will be a line not a quadratic.