Respuesta :
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.
we have
[tex](3x^{2} -2y^{2}+5x)+(4 x^{2}+12y^{2}-7x)[/tex]
Combine like terms
[tex](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[/tex]
therefore
the answer is the option C
He combined the terms [tex]-2y^{2}[/tex] and [tex]12y^{2}[/tex] incorrectly