I am obligated to do some exercises from some Russian maths book and I solved them, but the teacher told us to use the smartest possible way to achieve this and I guess mine aren't sneaky enough and my teacher won't be proud of me. So I came up with an idea to cheat a bit and ask u guys for some ideas. I hope you will be eager to help me :)
So these are equations I have a problem with:
Here is another one that I think is much harder. I can't solve it. I would be very grateful for your time and help.$$12(x+y)^2+x=2.5-y\\ 6(x-y)^2+x=0.125+y$$
I don't need whole solutions, I already got them and spent hours solving like 20 of similiar ones. I just need some smart and sneaky ideas from you guys there's a lot of short multiplication formulas knowledge and usage.
For #$6087$ : divide the $1$st by the $2$nd equation we have $x^2+y^2=2.5xy$. Let $y = tx$ then $x = 0$ or $t^2 + 1 = 5t$ .For #$6091$ you can use the same trick.