Question

a) -11x2 + 44 = 0        b)  x2 + 100 = 0       c)15x2 – 45x = 0    d) 72x2 + 81x = 0            

e) x2 – 8x +
12 = 0      f) 2x2 – 5x –
3 = 0        g) 5x2 –
3x + 1 = 0  

Answer 1

a)-11x+46=x=46/11=4,18

Answer 2

a) -11x² + 44 = 0 
-11x² = - 44
x² = - 44/ - 11
x = √4
x = 2

b) x² + 100 = 0
x² = - 100
x = ± √100
x = ± 10

c) 15x² – 45x = 0
x(15x - 45) = 0
x = 0
15x - 45 = 0
15x = 45
x = 45/15
x = 3   S= {0 , 3}

d) 72x² + 81x = 0
x (72x + 81) = 0
x = 0   

72x + 81 = 0
72x = 81
x = 81/72
x = 9/8
S = {0, 9/8}

e) x² – 8x +12 = 0  
∆ = 8^2 - 4 * 1 * 12
∆ = 64 - 48
∆ = 16

√∆ = 4

x' = (8 + 4)/2
x' = 6

x" = (8 - 4)/2
x" = 2

S = {2, 6}

 f) 2x² – 5x –3 = 0 
a= 2 
b= 5 
c= -3 

Δ= b²-4ac 
Δ= 5²-4.2.(-3) 
Δ= 25-4.2.(-3) 
Δ= 25-8.(-3) 
Δ= 25+24 
Δ= 49 


x= -b±√∆/2a 
x= -5±√49/2.2 
x= -5±7/4 

x' = -5+7/4 = 2/4 = 1/2 
x'' = -5-7/4 = -12/4 = -3 

S = {1/2,-3} 

g) 5x² –3x + 1 = 0  

x²-3x-2=0 
Δ= b² - 4ac 
Δ= (-3)² - 4*5(-2)
Δ= 9 + 40= 49  
Δ= 49 


x= - b ± √∆ / 2a 
x= - (- 3) ± √49 / 2*5 
x' = 3+7 / 10
x'= 10/10 = 1 

x" = 3 - 7 / 10
x"= -4/10=-2/5

S = {1/2,-3}