Respuesta :
Answer:
3t-21
2t²-6t
-3st-15s
9-x²
16x²-49
Step-by-step explanation:
In general
A(B+C)=AB+AC
(A+B)(D+C)=AD+AC+BD+BC
(A+B)(A-B)=A²+AB-BA-B²=A²-B²
ANSWER:
1) 3(t-7)
= 3t-21
2) 2t(t-3)
= 2t^2-6t
3) -3s(t+5)
= -3st-15s
4) (3+x)(3-x)
= 9-3x+3x-x^2
5) (4x-7)(4x+7)
= 16x^2 -28x+ 28x-49