Question

A teacher asked Tyrese to find the value of 2n

2 – 3n when n = 3

Here is his working.

2 × 32 – 3 × 3

= 62 – 9

= 36 – 9

= 27

What mistake has Tyrese made?​

Answer 1

Tyrese did not follow the order of operations (PEMDAS) and carry out the exponent first.

Explanation:

Tyrese's workings:

2 × 3² - 3 × 3

= 6² - 9

= 36 - 9

= 27

The mistake Tyrese made was that he didn't follow the order of operations (PEMDAS) and carry out the exponent first.

Correct workings:

Substitute n = 3 into the given expression:

= 2 × 3² - 3 × 3

Carry out the exponent first:

= 2 × 9 - 3 × 3

Now carry out the multiplications:

= 18 - 9

Finally, subtract:

= 9