Question

alguém pode me ajudar?​

Answer 1

4)

$\frac{28}{x} = \frac{20}{25} | \frac{7}{x} = \frac{5}{25} | \frac{7}{x} = \frac{1}{5}$

x=35

5)

$\frac{x}{4} = \frac{2}{x + 2}$

x²+2x=8

x²+2x-8=0

∆=4+32

∆=36

x=(-2±6)/2

x'=-8/2=-4

x"=4/2=2

6)

$\frac{x + 2}{x} = \frac{2x + 7}{x + 6}$

(x+2)•(x+6)=x•(2x+7)

x²+6x+2x+12=2x²+7x

x²-2x²+6x+2x-7x+12=0

-x²+x+12=0

∆=1+48

∆=49

x=(-1±7)/-2

x'=6/-2=-3

x"=-8/-2=4