Question

quais sao as raizes das equaçoes? 
a) x²+3x-28=0?

Answer 1

x²+3x-28=0
a= 1 b=3 c= -28

Δ=b²-4ac
Δ= (3)²-4·1·(-28)
Δ= 9 - (-112)
Δ=121

x= -b+/-√Δ/2a
x= -3 +/-√121/2·1
x= -3+/- 11/2

x'= 4
x''=-7

S:[-7,4]

Answer 2

$\Delta=b^2-4.a.c \\ \\ \Delta=3^2-4.1.(-28)=9+112=121 \\ \\ x=\frac{-b+-\sqrt{\Delta}}{2a}\\ \\ x=\frac{-3+-\sqrt{121}}{2}=\frac{-3+-11}{2} \\ \\ \boxed{x_1=\frac{-3-11}{2}=-7} \\ \\ \boxed{x_2=\frac{-3+11}{2}=\frac{8}{2}=4} \\ \\ \boxed{S=\{-7,4\}}$