Big Ideas Math Algebra 1, 2015
BI
Big Ideas Math Algebra 1, 2015 View details
5. Solving Quadratic Equations Using the Quadratic Formula
Continue to next subchapter

Exercise 4 Page 515

Practice makes perfect
a For this exercise, we need to identify our values for a, b, and c, then substitute them into the Quadratic Formula. Let's start by identifying the parts of a standard quadratic.
ccc ax^2&+& bx&+&c &=& 0 ↕ & & ↕ & & ↕ & & ↕ 1x^2&+& 2x& + & (-3)&=&0Now, let's substitute a= 1, b= 2, and c = -3 into the Quadratic Formula.
x^2+2x-3=0
x=-( 2) ± sqrt(( 2)^2-4 * 1(- 3))/2 * 1
â–Ľ
Simplify right-hand side
x=-2 ± sqrt(4-(-12))/2
x=-2 ± sqrt(16)/2
x=-2 ± 4/2
The solutions for this equation are x= - 2± 42. Let's separate them into the positive and negative cases.
x=- 2± 4/2
x_1=- 2+4/2 x_2=- 2-4/2
x_1=2/2 x_2=- 6/2
x_1=1 x_2=- 3

Using the Quadratic Formula, we found that the solutions of the given equation are x_1=1 and x_2=- 3.

b For this exercise, we also need to identify our values for a, b, and c, then substitute them into the Quadratic Formula. Let's start by identifying the parts of a standard quadratic.
ccc ax^2&+& bx&+&c &=& 0 ↕ & & ↕ & & ↕ & & ↕ 1x^2&+&( -4)x& + & 4&=&0 Now, let's substitute a= 1, b= -4, and c = 4 into the quadratic formula.
x^2-4x+4=0
x=-( -4) ± sqrt(( -4)^2-4 * 1(4))/2 * 1
â–Ľ
Simplify right-hand side
>x=4 ± sqrt((-4)^2-4 * 1(4))/2 * 1
x=4 ± sqrt(16-16)/2
x=4 ± sqrt(0)/2
x=4 ± 0/2
x=4/2
x=2
The formula shows that our solution for x is 2.
c For this exercise, again we need to identify our values for a, b, and c, then substitute them into the Quadratic Formula. Let's start by identifying the parts of a standard quadratic.
ccc ax^2&+& bx&+&c &=& 0 ↕ & & ↕ & & ↕ & & ↕ 1x^2&+& 4x& + & 5&=&0 Now, let's substitute a= 1, b= 4, and c = 5 into the quadratic formula.
x^2+4x+5=0
x=-( 4) ± sqrt(( 4)^2-4 * 1(5))/2 * 1
x=-4 ± sqrt(16-20)/2
x=4 ± sqrt(-4)/2
Since sqrt(-4) has no real solution, we will not calculate this any further.