p.15 問1

(1)	$$ (2x+y)\times 7x=14x^2+7xy $$
(2)	$$ (3a-b)\times 4a=12a^2-4ab $$
(3)	$$ (5a-6b)\times (-2b)=-10ab+12b^2 $$
(4)	$$ 4x(2x-1)=8x^2-4x $$
(5)	$$ 2x(x+3y)=2x^2+6xy $$
(6)	$$ -3a(8a+7b)=-24a^2-21ab $$
(7)	$$ -2x(-3x+2y)=6x^2-4xy $$
(8)	$$ (x-3y-2)\times 4x=4x^2-12xy-8x $$
(9)	$$ -3x(4x-3y+2)=-12x^2+9xy-6x $$
(10)	$$ 3a(-a+2b-1)=-3a^2+6ab-3a $$

p.15 問２

(1)	$$ \begin{align} (5x^2-10x)\div 5x &=5x^2\div 5x -10x\div 5x \\ &=\frac{5x^2}{5x}-\frac{10x}{5x} \\ &=\frac{5\times x\times x}{5\times x}-\frac{10\times x}{5\times x} \\ &=\frac{\bcancel 5\times \bcancel x\times x}{\bcancel 5\times \bcancel x}-\frac{ ^2 \bcancel{10}\times \bcancel x}{\bcancel 5\times \bcancel x} \\ &=x-2 \end{align}$$ $$ \left[ \begin{align} (5x^2-10x)\div 5x &=(5x^2-10x)\times \frac{1}{5x} \\ &=5x^2\times \frac{1}{5x} - 10x\times \frac{1}{5x} \\ &=x-2 \end{align} \right]$$
(2)	$$ (8a^2-2a)\div 2a=4a-1 $$
(3)	$$ (6ax-3ay)\div (-3a)=-2x+y $$
(4)	$$ \begin{align} (-10x^2+x)\div \frac{x}{2} &=(-10x^2+x)\times \frac{2}{x} \\ &=-20x+2 \end{align} $$
(5)	$$ \begin{align} (3x^2+6xy)\div \left( -\frac{3}{4}x \right) &=(3x^2+6xy)\div \left( -\frac{3x}{4} \right) \\ &=(3x^2+6xy)\times \left(-\frac{4}{3x} \right) \\ &=-4x-8y \end{align} $$
(6)	$$ \begin{align} (15x^2y-9xy^2)\div \frac{3}{2}xy &= (15x^2y-9xy^2)\times \frac{2}{3xy} \\ &=10x-6y \end{align} $$