Question

fie ecuatia x la a 2 +5x+4=0 cu radacinile x1,x2 apartine lui R sa se calculeze 3 x1 x2-4(x1+x2)

Answer 1

x²+5x+4=0
Δ=b²-4ac
Δ= 25-16=9
√Δ= 3
x1= -b+√Δ/ 2a
x1= -5+ 3 supra 2=>x1= -1
x2= -5-3 supra 2a=>x2= -8/2 =>x2=  -4
3x1*x2-4(x1+x2)
3*(-1)*(-4) - 4[ -1+ (-4) ]
+12 - 4 *(-5)
+12 -(-20)
+12 + 20 =32 

Answer 2

$Din~relatiile~lui~Viete~avem: \\ \\ x_1+x_2=- \frac{b}{a}=- \frac{5}{1}=-5. \\ \\ x_1 \cdot x_2= \frac{c}{a} = \frac{4}{1}=4. \\ \\ 3 x_1 x_2-4(x_1+x_2)=3 \cdot 4-4 \cdot (-5)=12+20=32.$