simplify sqrt(-2)*sqrt(-8)
Let's reduce: -2×-8
ⓘ In ℂ, the principal square root of a negative real number is i times the square root of its absolute value, because i² = -1: -2 = i×2, -8 = i×2×2
i×2×i×2×2
ⓘ Multiplying powers with the same base adds the exponents: i×2×i×2×2 = i2×212 + 1 + 12
i2×212 + 1 + 12
ⓘ i^2 = -1, so the powers of i reduce to 1, i, -1 or -i: i2 = -1■To add fractions, put them over the same denominator, then add the numerators: 12 + 1 = 1 + 22■Multiplying by -1 gives the opposite: -1×21 + 22 + 12 = -212 + 1 + 22
-212 + 1 + 22
ⓘ The numerator and the denominator are computed before the division: 1 + 2 = 3
-212 + 32
ⓘ To add fractions, put them over the same denominator, then add the numerators: 12 + 32 = 1 + 32
-21 + 32
ⓘ The numerator and the denominator are computed before the division: 1 + 3 = 4
-242
ⓘ We simplify the fraction by dividing the numerator and the denominator by 2, their greatest common divisor: 42 = 2
-22
ⓘ Without parentheses, the minus sign is not part of the power■An integer power is a repeated product: -22 = -(2×2) = -4
▶Simplified form:   -4