Answer:
1.
![(y - 5)(x + y)](https://img.qammunity.org/2021/formulas/mathematics/middle-school/zy5lm52est6wui1g1m8g1lkk31scls93kg.png)
2.
![{(x - y)}(x - y + a)](https://img.qammunity.org/2021/formulas/mathematics/middle-school/17rggyzzco3izwjbryvhkgz8nq7mdlp388.png)
3.
![(b - 3)(5b - 17)](https://img.qammunity.org/2021/formulas/mathematics/middle-school/5ouji1br4mbzt58n6zugt5dcaa2ai08n8x.png)
Explanation:
1. The given polynomial is
![x(y - 5) - y(5 - y)](https://img.qammunity.org/2021/formulas/mathematics/middle-school/3f3hfseai067j8a0iu7td79zrfvav0xuxe.png)
We need to factor the second part to get:
![x(y - 5) + y(y - 5)](https://img.qammunity.org/2021/formulas/mathematics/middle-school/pcmlk1i0hdsv92hcykqd01fbfa4frp3lpt.png)
We factor y-5 to obtain:
![(y - 5)(x + y)](https://img.qammunity.org/2021/formulas/mathematics/middle-school/zy5lm52est6wui1g1m8g1lkk31scls93kg.png)
2. We have
![{(x - y)}^(2) - a(y - x)](https://img.qammunity.org/2021/formulas/mathematics/middle-school/j1mb799h3utmnbxouox1kogpb70n4bhyiq.png)
We again factor -1 from the second part to get:
![{(x - y)}^(2) + a(x- y)](https://img.qammunity.org/2021/formulas/mathematics/middle-school/j8cw0kf7i5pn563bi50g66j746egv8kcxf.png)
We now factor x-y to get:
![{(x - y)}^(2) + a(x- y)](https://img.qammunity.org/2021/formulas/mathematics/middle-school/j8cw0kf7i5pn563bi50g66j746egv8kcxf.png)
![{(x - y)}(x - y + a)](https://img.qammunity.org/2021/formulas/mathematics/middle-school/17rggyzzco3izwjbryvhkgz8nq7mdlp388.png)
3. We have
![2(3 - b) + 5 {(b - 3})^(2)](https://img.qammunity.org/2021/formulas/mathematics/middle-school/f4uhu5dghzx3okdn4wxsla46fuf3qs6akz.png)
We factor negative 1 from the first part to get
![- 2(b - 3) + 5 {(b - 3})^(2)](https://img.qammunity.org/2021/formulas/mathematics/middle-school/1bvhpiidc72tnog5cpzrsd4sa0op22uwd7.png)
We now factor b-3 to get:
![(b - 3)( - 2 + 5(b - 3))](https://img.qammunity.org/2021/formulas/mathematics/middle-school/zfyqhasccnsxc7dlhobz1vws0j2fvtsuj0.png)
We now simplify to get:
![(b - 3)( - 2 + 5b - 15) = (b - 3)(5b - 17)](https://img.qammunity.org/2021/formulas/mathematics/middle-school/w4tslf5o17thprq05uwf5r4ikts88j2m4v.png)