zad.1
W(x)=x³+ax²-4x+b
P(x)=x³+(2a+3)x²+(a+ b+ c)x-1
a = 2a + 3
a-2a = 3
-a = 3
a= -3
b = -1
-4 = a+ b+ c
-4 = -3-1 +c
-4 = -4 +c
c = 0
odp: a= -3, b= -1, c=0
dla a=3 i b=0:
W(x) = x³ + 3x² -4x = x( x² + 3x -4)
Δ = 9 + 16 = 25
√Δ = 5
x₁ = -3 -5 / 2 = -8/2 = -4
x₂ = -3 + 5 / 2 = 2/2 = 1
W(x) = x(x-1)(x+4)
zad.2
W(x)=x³+mx²+x+n
W(1)=-5 W(-1)=-9
1³ + m*1² + 1 + n = -5
(-1)³ + m * (-1)² -1 +n = -9
m + n = -7
m = -7-n
zad.3
W(x)=2x³+ax²+bx+30
W(3) = 0 i W(-1) = 0
2 * 27 + a * 9 + b * 3 + 30 = 0
2 * (-1) + a * 1 -b + 30 = 0
9a + 3b = -84 /(:3)
a -b = -28
3a +b = -28
a -b = -28
4a = -56
a = -14
-14 -b = -28
b = 14
a=-14
b=14