a) Thể tích không khí bên trong chiếc lều:

\(\frac13.3^2.2,8=8,4\left(m^3\right)\)

b) Diện tích đáy:

3.3 = 9 (m²)

Độ dài cạnh bên của lều:

√(2,8² + 1,5²) ≈ 3,18 (m)

Diện tích vải lều:

9 + 4 . 3 . 3,18 : 2 = 28,08 (m²)

Số tiền mua vải:

28,08 . 15000 - 28,08 . 15000 . 5% = 400140 (đồng)

a) \(x y + y^{2} - x - y\)

\(= \left(\right. x y + y^{2} \left.\right) - \left(\right. x + y \left.\right)\)

\(= y \left(\right. x + y \left.\right) - \left(\right. x + y \left.\right)\)

\(= \left(\right. y - 1 \left.\right) \left(\right. x + y \left.\right)\)

b) \(\left(\left(\right. x^{2} y^{2} - 8 \left.\right)\right)^{2} - 1\)

\(= \left(\left(\right. x^{2} y^{2} - 8 \left.\right)\right)^{2} - 1^{2}\)

\(= \left(\right. x^{2} y^{2} - 8 - 1 \left.\right) \left(\right. x^{2} y^{2} - 8 + 1 \left.\right)\)

\(= \left(\right. x^{2} y^{2} - 9 \left.\right) \left(\right. x^{2} y^{2} - 7 \left.\right)\)

\(= \left(\right. x y + 3 \left.\right) \left(\right. x y - 3 \left.\right) \left(\right. x^{2} y^{2} - 7 \left.\right)\)

a) \(\left(\right. - 12 x^{13} y^{15} + 6 x^{10} y^{14} \left.\right) : \left(\right. - 3 x^{10} y^{14} \left.\right)\)

\(= - 12 x^{13} y^{15} : - 3 x^{10} y^{14} + 6 x^{10} y^{14} : - 3 x^{10} y^{14}\)

\(= 4 x^{3} y - 2\)

b) \(\left(\right. x - y \left.\right) \left(\right. x^{2} - 2 x + y \left.\right) - x^{3} + x^{2} y\)

\(= x^{3} - 2 x^{2} + x y - x^{2} y + 2 x y - y^{2} - x^{3} + x^{2} y\)

\(= - 2 x^{2} + 3 x y - y^{2}\)