Question

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

Answer 1

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

Answer 2

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.