Question

A student concluded that the inequality −3+2y≤4x is equivalent to the inequality y≥2x+32, as shown below. Describe and correct the student’s error.

Answer 1

Answer:

$-3 +2y \leq 4x$

$2y \leq 4x+3$

$y \leq 2x + \frac{3}{2}$

And that's different from the claim of the student that:

$y \geq 2x +\frac{3}{2}$

The error of the student is that he/she changes the sign of the inequality from $\leq$ to $\geq$ and that's not possible since we don't multiply both sides of the equation by -1

Step-by-step explanation:

For this case we have the following inequality:

$-3 +2y \leq 4x$

We want to rewrite the last expression with y in the left and x in the right so we can begin adding 3 in both sides of the inequality and we got:

$2y \leq 4x+3$

Now we can divide both sides of the inequality by 2 and we got:

$y \leq 2x + \frac{3}{2}$

And that's different from the claim of the student that:

$y \geq 2x +\frac{3}{2}$

The error of the student is that he/she changes the sign of the inequality from $\leq$ to $\geq$ and that's not possible since we don't multiply both sides of the equation by -1