S soprano New member Joined Jan 29, 2010 Messages 12 May 14, 2010 #1 5a+b=4 b=40-a^2 This is what I have done so far: 5a+40-a^2=4 a(5-a)=-36 I totally don't know what I am doing.
5a+b=4 b=40-a^2 This is what I have done so far: 5a+40-a^2=4 a(5-a)=-36 I totally don't know what I am doing.
G galactus Super Moderator Staff member Joined Sep 28, 2005 Messages 7,203 May 14, 2010 #2 Sub b into the first equation. This gives: \(\displaystyle 5a+40-a^{2}=4\) Rearrange to make a nice quadratic: \(\displaystyle a^{2}-5a-36=0\) Now factor away.
Sub b into the first equation. This gives: \(\displaystyle 5a+40-a^{2}=4\) Rearrange to make a nice quadratic: \(\displaystyle a^{2}-5a-36=0\) Now factor away.
S soprano New member Joined Jan 29, 2010 Messages 12 May 14, 2010 #3 so a=-4 or a=9 correct? would the answer be written (-4,9)
G galactus Super Moderator Staff member Joined Sep 28, 2005 Messages 7,203 May 14, 2010 #4 Just write it as a=9 or a=-4. Written the other way makes it look like corrdinates.
