Question

Resolva as equações incompletas:
a) (x-7).(x-3)+10x=30
b)2x.(x+1)=x.(x+5)+3.(12-x)

Answer 1

a) (x-7). (x-3)+10x=30
....x^2-3x-7x+21+10x=30
....x^2+21=30
....-x^2+9

b) 2x^2+2x=x^2+5x+36-3x

x^2+5x+36-3x-2x^2-2x

-x^2+3x+36-3x

-x^2+36

Answer 2

a) (x - 7) . (x - 3) + 10x = 30

x² -10x + 21 + 10x = 30
x² - 10x + 10x = 30 - 21
x² = 9

x = ± √9

x' = -3
x'' = 3

S = {-3, 3}

===
b) 2x . (x + 1) = x .(x + 5) + 3.(12 -x)

2x² + 2x = x² + 5x + 36 - 3x
2x² + 2x = x² + 2x + 36
2x² + 2x - x² - 2x = 36
2x² - x² + 2x - 2x = 36
x² = 36

x = ± √36

x' = -6
x'' = 6

S = {-6,  6}