Question:
9x – ……………….. = – 21 has the solution (- 2).
Solution:
Let 9x-m= -21 has the solution (-2).
Since, $x=-2$ is the solution of the equation.
$\therefore$ $9 \times(-2)-m=-21$
$\Rightarrow$ $-18-m=-21$ [transposing $-21$ to LHS and $-m$ to RHS]
$-18+21=m$
$\Rightarrow$ $m=3$
Hence, $9 x-3=-21$ has the solution $(-2)$.
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