<p>pg 475 #12
If x^2-y^2=77 and x+y=11, what is the value of x?</p>
<p>i just plugged in numbers until i got 9. :P
is there an easier way to do this or do we have to plug in numbers?</p>
<p>Difference of squares...so (x-y)(x+y)=77
Plug in..
11(x-y)=77
x-y=7
x+y=11
Add the equations together..
2x=18
x=9</p>