Martina has answered some questions on algebra - OCR - GCSE Maths - Question 3 - 2019 - Paper 1

Martina incorrectly simplified the expression. Instead of arriving at $x^6$, she should have applied the law of exponents: $\frac{x^{10}}{x^{2}} = x^{10 - 2} = x^{8}.$ Thus, the correct answer is:

$x^{8}$

Martina's mistake was with the substitution of values in the equation and miscalculating the expression. The correct substitution yields:

$s = 0 \times 5 + \frac{1}{2} \times 6 \times 5^{2} = 0 + \frac{1}{2} \times 6 \times 25 = 75.$ Therefore, the correct answer is:

$s = 75$