(3x²-2y²+5x)+(4x²+12y²-7x)
This is all about combining like terms.
(7x²+10y²-2x) is what I got.
(7x-10y-2x) is what Marcus got.
Marcus didn't add the squared symbol for 10y and he added a negative sign for 10y. He did -10y but it is +10y² because -2y²+12y²=10y². So, his problem is that Marcus didn't add right.
Hope this helps.
If it does, I would appreciate a brainliest rank.
<3
