Proof of any number is equal to any different number and therefore math is pointless

a, b distinct

then t = a + b
then t(a - b) = a² - b²
then ta - tb = a² - b²
then a² - ta = b² - tb
then complete the square on each side
and a² - ta + t²/4 = b² - tb + t²/4
and (a - t/2)² = (b - t/2)²
and a - t/2 = b - t/2
and a = b
QED

QUESTION: What is the earliest reference to this 'proof'?