Difference between revisions of "1955 AHSME Problems/Problem 47"

(Solution)
(Solution)
Line 9: Line 9:
 
<cmath>a + bc = a^2 + ab + ac + bc</cmath>
 
<cmath>a + bc = a^2 + ab + ac + bc</cmath>
 
<cmath>a = a^2 + ab + ac</cmath>
 
<cmath>a = a^2 + ab + ac</cmath>
These expressions are equal only when <math>\boxed{\text{(C) equal only when} a + b + c = 1.}</math>
+
These expressions are equal only when <math>\boxed{\text{(C) equal whenever } a + b + c = 1.}</math>
  
 
== See Also ==
 
== See Also ==

Revision as of 20:52, 24 July 2022

Problem 47

The expressions $a+bc$ and $(a+b)(a+c)$ are:

$\textbf{(A)}\ \text{always equal}\qquad\textbf{(B)}\ \text{never equal}\qquad\textbf{(C)}\ \text{equal whenever }a+b+c=1\\ \textbf{(D)}\ \text{equal when }a+b+c=0\qquad\textbf{(E)}\ \text{equal only when }a=b=c=0$

Solution

Using the FOIL method, we see that $(a+b)(a+c) = a^2 + ab + ac + bc.$ We want to solve \[a + bc = a^2 + ab + ac + bc\] \[a = a^2 + ab + ac\] These expressions are equal only when $\boxed{\text{(C) equal whenever }  a + b + c = 1.}$

See Also

1955 AHSC (ProblemsAnswer KeyResources)
Preceded by
Problem 46
Followed by
Problem 48
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
All AHSME Problems and Solutions


The problems on this page are copyrighted by the Mathematical Association of America's American Mathematics Competitions. AMC logo.png