# [LON-CAPA-users] Extracting the numerical value from a solve()Maxima command

Seema Ali sali at vsb.bc.ca
Wed Feb 8 21:29:08 EST 2012

```I believe I asked about this question before and made changes so that it would extract the user's response and plug it into a formula to see if both sides are equal.  Unfortunately the question produces a weird error sometimes when calculating the solution.

I can't tell what is causing the error.  It works with other negative solutions.

Thanks.

ERROR: Computer's answer is incorrect ("-1.24"). It is likely that the tolerance range [-1.24200376392202, -1.24000376392203] needs to be adjusted.
This error occurred while processing response 1_7 in part 0

The answer to the question is correct:
Solve for \$x\$ to the nearest hundredth where \$6^{3 x} = 9^{-4 x - 8}\$

<problem>
<script type="loncapa/perl">
\$base1 = &random(2,9,1);
do {
\$base2 = &random(2,9,1);
} while (\$base1==\$base2);
\$a = &random(2,3,1);
\$b = &random(-7,-4,1);
\$c = &random(1,10,1);

if (&random(0,1,1)) {
\$power1 = "\$a x";
\$power2 = "\$b x - \$c";
\$power1maxima = "\$a * x";
\$power2maxima = "\$b * x - \$c";
} else {
\$power1 = "\$a x + \$c";
\$power2 = "\$b x";
\$power1maxima = "\$a * x + \$c";
\$power2maxima = "\$b * x";
}

\$solution = &cas('maxima',"float(solve((\$power1maxima)*log(\$base1) = (\$power2maxima)*log(\$base2),x))");
\$solution=~/\=\s*(.+)\s*\]/;
</script>
<startouttext />Solve for <m>\$x\$</m> to the nearest hundredth where <m eval='on'>\[\$base1^{\$power1} = \$base2^{\$power2}\]</m>
<br /><endouttext />