9. I. 4x^2+16x+9=0
a=4, b=16, c-9
Δ=b^2-4ac
Δ=256-4*4*9
Δ=256-144
Δ=112
x1=(-16+V112)/8=(-16+4V7)/8= - 2+V7/2
x2=(-16-V112)/8=(-16 - 4V7)/8= (- 2- V7/2
II. 4x^2+16x+9= 4(x^2+4x+4)-7=2^2(x+2)^2-V7^2=[2(x+2)-V7][2(x+2)+V7]=0
⇒2(x+2)-V7=0, 2(x+2)=V7, x+2=V7/2, x= -2+V7/2
2(x+2)+V7=0, x+2=-V7/2, x= -2-V7/2
b) x1= -2+1,3
x1= - 0,7
x2= -2-1,3
x2= -3,3
10. c. x1=-2, x2=4
f(x)=(X+2)(x-4)=x^2-2x-8
a. V(-b/2a, -Δ/4a)
V(2/2, -(4+4*8)/4 ), V(1, -9)
b. x= -b/2a, x=1 is the equation
d. y intercept (0,8)
11. f(x)= x^2 - 4x - 6
x 1= (4+V16+24)/2=(4+2V10)/2= 2+V10≈5,2
x2= 2- V10≈-1,2
x -3 -2 -1 0 1 2 3
f(x) 15 6 -1 -6 -9 -10 -9
