Question

Resolva as equações:


a) -2x – 5 = -9 

b) -5x + 9 = 2x - 12 

c) -x² - 5x - 4 = 0

 d) x² + 3x – 4 = 0

Answer 1

$a) -2x-5=-9</strong> \\ -2x=-9+5 \\ -2x=-4 \\ x= \frac{-4}{-2} \\ <strong><u>x=2$

$b)-5x+9=2x-12 \\ -5x-2x=-12-9 \\ -7x=-21 \\ x= \frac{-21}{-7} \\<strong><u> x=3$

c)-x²-5x-4=0
a=-1; b=-5; c=-4
∆=b²-4ac⇒ ∆=(-5)²-4.(-1).(-4)⇒ ∆=25-16⇒ ∆=9
x=-b±√∆ / 2.a⇒ x=-(-5)± √9 / 2.(-1)→ x=5±3 / -2
x'=5+3/-2⇒ x'=8/-2⇒ x'=-4
x"=5-3/-2⇒ x''=2/-2⇒ x''=-1
S={-4 , -1}

d)x²+3x-4=0
a=1; b=3; c=-4
Δ=b²-4ac⇒ Δ=(-3)²-4.1.(-4)⇒ Δ=9+16⇒ Δ=25
x=-b±√∆ / 2.a⇒ x=-3± √25 / 2.1→ x=-3±5 / 2
x'=-3+5/2⇒ x'=2/2⇒ x'=1
x''=-3-5/2⇒ x''=-8/2⇒ x''=-4
S={-4, 1}