In Q1, The equation k = y² + a is correct,
To make y the subject of the formula, √k = y + a is incorrect, it should be √k = y + √a
√k - √a = y
In Q2, t = v/4 + 1 is correct
t - 1 + v/4 is incorrect, it should be t - 1 = v/4
t - 1/4 = v
so the correct answer is t-1/4=v