The answer is Difference of Cubes.
Difference of cubes is a³ - b³.
27 can be written as 3³ (= 3 × 3 × 3 = 27). So, a = 3.
8 can be written as 2³ (= 2 × 2 × 2 = 8). So, b = 2.
Difference of cubes can be expressed as:
a³ - b³ = (a - b)(a² + ab + b²)
⇒ 3³ - 2³ = (3 - 2)(3² + 3×2 + 2²) = 1 × (9 + 6 + 4) = 1 × 19 = 19
⇒ 27 - 8 = 19
12 because if you take 2 and add it to 10 you get 12
Because angleCBD＋angleBDC＋angleC＝180
so angleCBD＋angleBDC＝180－angleC＝180－82＝98
because BC＝DC
so angleCBD＝angleBDC
so 2 angleCDB＝98
so angleCDB＝49
so y＝29
by Joy Xu，紫馨雪汐
