Question

Which of the following equations cannot be formed using the equation x = 7?

• A. 2x + 1 = 15
• B. 7x - 1 = 50
• C. x - 3 = 4
• D. $\frac{x}{7}-1=0$

Answer 1

The correct option is B 7x - 1 = 50

We have, x = 7
Put x = 7 in all the equations and equation which doesn't satisfy x = 7 can not be formed by taking x = 7.

(i) $2x+1=15$
Put x = 7
$2\times 7+1=15⟹15=15$
So, x = 7 satisfies the equation $2x+1=15$.
Hence equation $2x+1=15$ can be formed by taking x = 7.

(ii) $7x-1=50$
Put x = 7
$7\times 7-1=50$
$⟹48=50$, which is not true.
So, x = 7 does not satisfy equation $7x-1=50.$
Hence equation $7x-1=50$ can not be formed by taking x = 7.

(iii) $x-3=4$
Putting x = 7, we have
$7-3=4$, which is true.
So x = 7 satisfies the equation $x-3=4$.
Hence equation $x-3=4$ can be formed by taking x = 7.

(iv) $\frac{x}{7}-1=0$
Putting x = 7, we have
$\frac{7}{7}-1=0$, which is true.
So x = 7 satisfies the equation $\frac{x}{7}-1=0.$
Hence equation $\frac{x}{7}-1=0$ can not be formed by taking x = 7.