Difference between revisions of "1950 AHSME Problems/Problem 6"

m
 
(2 intermediate revisions by one other user not shown)
Line 23: Line 23:
 
==See Also==
 
==See Also==
  
{{AHSME box|year=1950|num-b=5|num-a=7}}
+
{{AHSME 50p box|year=1950|num-b=5|num-a=7}}
[[Categroy:Introductory Algebra Problems]]
+
[[Category:Introductory Algebra Problems]]
 +
{{MAA Notice}}

Latest revision as of 10:57, 5 July 2013

Problem

The values of $y$ which will satisfy the equations $2x^{2}+6x+5y+1=0, 2x+y+3=0$ may be found by solving:

$\textbf{(A)}\ y^{2}+14y-7=0\qquad\textbf{(B)}\ y^{2}+8y+1=0\qquad\textbf{(C)}\ y^{2}+10y-7=0\qquad\\ \textbf{(D)}\ y^{2}+y-12=0\qquad \textbf{(E)}\ \text{None of these equations}$

Solution

If we solve the second equation for $x$ in terms of $y$, we find $x=-\dfrac{y+3}{2}$ which we can substitute to find:

\[2(-\dfrac{y+3}{2})^2+6(-\dfrac{y+3}{2})+5y+1=0\]

Multiplying by two and simplifying, we find:

\begin{align*} 2\cdot[2(-\dfrac{y+3}{2})^2+6(-\dfrac{y+3}{2})+5y+1]&=2\cdot 0\\ (y+3)^2 -6y-18+10y+2&=0\\ y^2+6y+9-6y-18+10y+2&=0\\ y^2+10y-7&=0 \end{align*}

Therefore the answer is $\boxed{\textbf{(C)}\ y^{2}+10y-7=0}$

See Also

1950 AHSC (ProblemsAnswer KeyResources)
Preceded by
Problem 5
Followed by
Problem 7
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