Solving quadratics by factoring

Solve:   $5x^2-45=0$  

•  $x=3$  

•  $x=-3$  

•  $x=3$  and  $x=-3$  

•  $x=0$  ,  $x=3$  , and  $x=-3$  

Solve:  $0=3x^2-12x-15$  

•  $x=-5$  and  $x=1$  

•  $x=5$  and  $x=-1$  

•  $x=0$  ,  $x=5$  , and  $x=-1$  

•  $x=-5$  and  $x=-1$  

What is the first question you ask yourself when factoring a polynomial? 

• How many terms does it have? 
• Is there a GCF? 
• What strategy should I use? 
• Why do I have to learn this?!?!?!

Factor Completely: 
3x² + 18x +15
Hint: Factor GCF first.

• 3(x² + 6x + 5)
• (x + 5)(x + 1)
• 3(x + 5)(x + 1)
• Prime

Factor
k² - 2k - 24

• (k+4)(k-6)
• (k+4)(k+6)
• (k+6)(k-1)
• (k-4)(k+6)

Factor
3v² - 4v - 7

• (3v-7)(v+1)
• 3(v-7)(v-1)
• (3v+1)(v-9)
• (3v+1)(v-10)

What is the first step in solving 
(x + 2)(x - 3) = 0      ?

• Plug in zero for x
• Solve for x
• FOIL
• Set each binomial factor equal to zero

What are the values of x when y = 0?

• { -3, 1 }
• { -2 }
• { -3, -1 }
• { 1, 3 }

What are the x- intercepts?

• x= 0 and x= -4
• x= 0 and x= 4
• y= 0
• x= 2

Solve by factoring: x² + 3x - 18 = 0

• x = -3 and x = 6
• x = 3 and x = -6
• x = -9 and x = 2
• x = 9 and x = -2