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 1.  Let f(a,b) = 2a - 3b^2 + 7. If f(b,3) = 90, then what is b?

 

2.  Suppose a(x) = 3x - 7 and b(x) = 2 - x^3. Find a(b(3)) - b(a(3)).

 

Thanks :D

 Nov 4, 2017

Best Answer 

 #1
avatar+7477 
+2

1)

f(b,3) = 2b - 3(3)^2 + 7  = 2b - 20

 

2b - 20 = 90

2b = 110

b = 55

 

2)

b(3) = 2 - 3^3 = -25

a(3) = 3(3) - 7 = 2

 

a(b(3)) - b(a(3))

= a(-25) - b(2)

= 3(-25) - 7 - (2 - 2^3)

= -75 - 7 + 6

= -76

 Nov 4, 2017
 #1
avatar+7477 
+2
Best Answer

1)

f(b,3) = 2b - 3(3)^2 + 7  = 2b - 20

 

2b - 20 = 90

2b = 110

b = 55

 

2)

b(3) = 2 - 3^3 = -25

a(3) = 3(3) - 7 = 2

 

a(b(3)) - b(a(3))

= a(-25) - b(2)

= 3(-25) - 7 - (2 - 2^3)

= -75 - 7 + 6

= -76

MaxWong Nov 4, 2017

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