Respuesta :

apologiabiology
6.
times both sides by 5
5a=b+c
minus b both sides
5a-b=c
c=5a-b


7.
distribute invibile -1
2x²+5x-4-3x²-7x+1
-1x²-2x-3
-x²-2x-3
irspow
a=(b+c)/5  multiply both sides by 5

5a=b+c  subtract b from both sides

c=5a-b

...

2x^2-3x^2+5x-7x-4+1

-x^2-2x-3