Question

Marcus finds that (3x^2-2y^2+5x)+(4x^2+12y-7x)= 7x^2-10y^2-2x What error did Marcus make?

A: He combined the terms 5x and –7x incorrectly.
B: He combined the terms 3x^2 and 4x^2 incorrectly.
C: He combined the terms –2y^2 and 12y^2 incorrectly.
D: He subtracted the polynomials instead of adding.

Answer 1

I believe the correct answer from the choices listed above is option C. The error that Marcus made would be that he combined the terms –2y^2 and 12y^2 incorrectly. It should be 10y^2 when combined not -10y^2. Hope this answers the question.

Answer 2

we have

`(3x^(2) -2y^(2)+5x)+(4 x^(2)+12y^(2)-7x)`

Combine like terms

`(3x^(2) -2y^(2)+5x)+(4 x^(2)+12y^(2)-7x)\\=(3x^(2)+4x^(2))+(-2y^(2)+12y^(2))+(5x-7x)\\=7x^(2) +10y^(2)-2x`

therefore

the answer is the option C

He combined the terms
`-2y^(2)` and
`12y^(2)` incorrectly