In case your expression is:
![x^2\:-\:xy\:+\:x^2\:-\:xy](https://img.qammunity.org/2021/formulas/mathematics/high-school/q1pmnjmabxvdbord06oualhq9h4ruoz8hu.png)
Solution:
Given the expression
![x^2\:-\:xy\:+\:x^2\:-\:xy](https://img.qammunity.org/2021/formulas/mathematics/high-school/q1pmnjmabxvdbord06oualhq9h4ruoz8hu.png)
Group like terms
![x^2\:-\:xy\:+\:x^2\:-\:xy=x^2+x^2-xy-xy](https://img.qammunity.org/2021/formulas/mathematics/high-school/ziwyqe08smknzz28n7t1yzve1pz1aycl85.png)
Add similar elements: x²+x² = 2x²
![=2x^2-xy-xy](https://img.qammunity.org/2021/formulas/mathematics/high-school/2m5qjr12bkec8gfze4dhcdfa2g63ibo3c7.png)
Add similar elements: -xy-xy = -2xy
![=2x^2-2xy](https://img.qammunity.org/2021/formulas/mathematics/high-school/a6kaiojbdc39r9g0sa5mvqhmkkzxvbzo4x.png)
Thus,
![x^2-xy+x^2-xy=2x^2-2xy](https://img.qammunity.org/2021/formulas/mathematics/high-school/xskwft5t62n33qm6jmzc3ezlp8yodyyv9o.png)
In case your expression is:
![\left(xx\right)^2\:-\:xy\:+\:x^2\:-\:xy](https://img.qammunity.org/2021/formulas/mathematics/high-school/rgu0umeexiedrgsarp9rvc4wvr1iqervxa.png)
Solution:
Given the expression
![\left(xx\right)^2\:-\:xy\:+\:x^2\:-\:xy](https://img.qammunity.org/2021/formulas/mathematics/high-school/rgu0umeexiedrgsarp9rvc4wvr1iqervxa.png)
Group like terms
![\left(xx\right)^2\:-\:xy\:+\:x^2\:-\:xy=x^2-xy-xy+\left(xx\right)^2](https://img.qammunity.org/2021/formulas/mathematics/high-school/4d1ft3tb3o4kcu9dx872wuyzcprztqjx7i.png)
Add similar elements: -xy-xy = -2xy
![=x^2-2xy+\left(xx\right)^2](https://img.qammunity.org/2021/formulas/mathematics/high-school/7uv01yn910dh5o64lpq8zej8gxjzhu8f5a.png)
as (xx)² = x⁴
so
![=x^2-2xy+x^4](https://img.qammunity.org/2021/formulas/mathematics/high-school/878f0hitilpou026u5t7hny07xwkhfo1lx.png)
Therefore, we conclude that: