SOLUTION: Equation (x+2)(x+a)=x^2 + 4x+b where a and b are constants. If the equation is true for all values of x, what's the value of b? A. 8 B. 6 C. 4 D. 2

Algebra ->  Finance -> SOLUTION: Equation (x+2)(x+a)=x^2 + 4x+b where a and b are constants. If the equation is true for all values of x, what's the value of b? A. 8 B. 6 C. 4 D. 2      Log On


   

Question 1088875: Equation (x+2)(x+a)=x^2 + 4x+b where a and b are constants. If the equation is true for all values of x, what's the value of b?
A. 8
B. 6
C. 4
D. 2
Answer by ikleyn(52764) About Me  (Show Source):
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If the highlight%28cross%28equation%29%29 equality   (x+2)(x+a)=x^2 + 4x+b   is true for all values of  x,  it implies that  a = 2. 
     (after opening the parentheses and comparing the terms)

In turn, it implies that  2a = b.  Hence,  b = 4.


Answer.  b = 4. Option C).