soal MTK ajabar

1. (x+5) (x+7)= x2+7x+3x+21
=x2+10x+21

2. (x+5) (x+4)= x2+5x+4x+20
=x2+9x+20

3. (x+13) (x+4)=x2+13x+4
=x2+17x+52-

4. (7+x)(10+x) =70+7x+10x+x2
=70+17x+x2

5. (x-2) (x+6) =x2-2x-6x-12
= x2-8x-12