Core Connections Algebra 2, 2013
CC
Core Connections Algebra 2, 2013 View details
Chapter Closure

Exercise 190 Page 435

a We want to solve the following system of equations.
y=2x & (I) y=x^2+5 & (II) Since the y-variable is already isolated in both equations, we will use the Substitution Method. This allows us to substitute its value x^2+5 from Equation (II) for y in Equation (I).
y=2x y=x^2+5
x^2+5=2x y=x^2+5
x^2+5-2x=0 y=x^2+5
Notice that in Equation (I) we have a quadratic equation in terms of only the x-variable. x^2+5-2x=0 ⇕ 1x^2+( - 2)x+ 5=0 We can substitute a= 1, b= - 2, and c= 5 into the Quadratic Formula.
x=- b±sqrt(b^2-4ac)/2a
x=- ( - 2)±sqrt(( - 2)^2-4( 1)( 5))/2( 1)
Solve for x
x=2±sqrt((- 2)^2-4(1)(5))/2(1)
x=2±sqrt(4-4(1)(5))/2(1)
x=2±sqrt(4-20)/2
x=2±sqrt(-16)/2
x=2±sqrt(16)* i/2
x=2± 4i/2
This result tells us that we have two solutions for x. One of them will use the positive sign and the other one will use the negative sign.
x=2± 4i/2
x_1=2+4i/2 x_2=2-4i/2
x_1=1+2i x_2=1-2i

Now, consider Equation (I). y=2x We can substitute x=1+2i and x=1-2i into the above equation to find the values for y.

x 2x y=2x
1+2i 2( 1+2i) 2+4i
1-2i 2( 1-2i) 2-4i

Therefore, the solutions to the system are (1+2i, 2+4i) and (1-2i, 2-4i).

b Let's take a look at the given system of equations once again.

y=2x y=x^2+5 Note that Equation (I) represents the equation of the line and Equation (II) — the equation of the quadratic function. The solutions to the system are the points where the graphs of the line and the parabola intersect. Solutions (1+2i, 2+4i), (1-2i, 2-4i) We can see that the coordinates of the points are complex numbers. Since there are no real-valued points of intersection, the graphs of the line and the parabola do not intersect on a coordinate plane.