<p>When you did
it gave you the right answer.</p>
<p>When solving by hand, after you plugged
y = (2x-5)/3
in
x^2 - y^2 = 77,
you most likely got
5x^2 + 20x + 25 = 693, or
5x^2 + 20x - 668 = 0
with x= 9.73 or -13.7.</p>
<p>It should be
5x^2 + 20x - 25 = 693, or
5x^2 + 20x - 718 = 0
with x = -14.15 or 10.15</p>
<p>Second part of my post just illustrates solving the system step by step.
Oops, I just noticed my mistype “solve(2x - 3y = 0, y)” in post #6.</p>
<p>Let’s start again:
solve(2x - 3y = 5, y)
[F4] 1
[Up Arrow key]
[ENTER]
[ENTER]</p>
<p>You see y=(2x-5)/3 (don’t type this line :)).</p>
<p>x^2 - y^2 - 77 = 0
[ENTER]</p>
<p>You see (5x^2)/9 + (20x)/9 - 718/9 = 0 (don’t type this line either :D).</p>
<p>solve(
[Up Arrow key]
[ENTER]
,x)
<a href=“to%20get%20an%20approximate%20answer”>DIAMOND key</a>
[ENTER]</p>
<p>That’s all.
I am not sure why you are getting
It’s possible that you mistyped something and got a quadratic equation with no real solutions, like in
solve(x^2 = -1, x).</p>
<p>To start from the scratch, do [F6] 2 first.</p>