a² - 13 = (a - √13)(a + √13)
15 - b² = (√15 - b)(√15 + b)
x² - 80 = (x - √80)(x + √80)x² - 80 = (x - 4√5)(x + 4√5)
a² - 13 = (a - √13)(a + √13)
15 - b² = (√15 - b)(√15 + b)
x² - 80 = (x - √80)(x + √80)
x² - 80 = (x - 4√5)(x + 4√5)