Lin says she can tell that 25 x^2+40x+16 and 49x^2-112x+64 are perfect squares because each expression has the following characteristics, which she saw in other perfect squares in standard form: The first term is a perfect square. The last term is also a perfect square. If we multiply a square root of the first term and a square root of the last term and then double the product, the result is the middle term. Show that has the characteristics Lin described. 11) The first term is a perfect square. 12) The last term is also a perfect square. 13) If we multiply a square root of the first term and a square root of the last term and then double the product, the result is the middle term.