Đáp án:
$a) (a+b+c)^2 -(b+c)^2-c^2$
$ = a^2+b^2+c^2+2ab+2ac+2bc - b^2-2bc-c^2 -c^2$
$ = a^2-c^2+2ab+2ac$
$b) (a+b-c)^2-(b-c)^2 = 2ab+2ac$
$ = a^2+b^2+c^2+2ab-2ac-2bc - b^2+2bc-c^2 -2ab-2ac$
$ = a^2-4ac$
a) $(a+b+c)^2-(b+c)^2-c^2$
$=a(a+b+c)+b(a+b+c)+c(a+b+c)-(b^2+2bc+c^2)-c^2$
$=a^2+ab+ac+ab+b^2+bc+ac+bc+c^2-b^2-2bc-c^2-c^2$
$=a^2+(ab+ab)+(ac+ac)+(bc+bc-2bc)+(c^2-c^2-c^2)+(b^2-b^2)$
$=a^2+2ab+2ac-c^2$
$=a^2-c^2+2ab+2ac$
b) $(a+b-c)^2-(b-c)^2$
$=a(a+b-c)+b(a+b-c)-c(a+b-c)-(b^2-2bc+c^2)$
$=a^2+ab-ac+ab+b^2-bc-ac-bc+c^2-b^2+2bc-c^2$
$=a^2+(b^2-b^2)+(c^2-c^2)+(ab+ab)+(-ac-ac)+(-bc-bc+2bc)$
$=a^2+2ab-2ac$
cho tam giác ABC nhọn H là trực tâm.Gọi I,K là trung điểm của AH,AB cắt AC và BC tại M,N và cắt nhau tại O a) C/m MN//IK b) c/m góc KIH =góc ONM c)c/m tam giác KHI=tam giác MON giúp mình câu b,c zới!!!
Từ nhận thức cề phong cách hcm,em có nhận xét gì về lỗi sống của thanh niên hiện nay và phương pháp đen luyện của bản thân để trở thành công dân toàn cầu. Ai giúp mk với mình cần gấp ạ
có 2 điện tích q1= + 2.10^-6 (C) , q2 = - 2.10^-6 (C), đặt tại hai điểm A, B trong chân không và cách nhau một khoảng 6 (cm). Một điện tích q3= +2.10^-6 (C). đặt trên đường trung trực của AB , cách AB một khoảng 4 cm . a) độ lớn của lực diện do 2 điện tích q1 và q2 tác dụng lên điện tích q3 là bXác định vị trí của q1 để lực đạt giá trị cực đại
Lm hộ mik mấy bài còn trống mik cần rất gấp
Mọi người ơi xin giúp mình với! 1 người gửi ngân hàng 200 triệu đồng kỳ hạn 1 năm.với lãi suất 6% năm. Sau 2 năm người đó đến ngân hàng rút tiền thì được bao nhiêu tiền cả gốc và lãi, biết số lãi mỗi năm nếu không rút thì được cộng vào vốn và tính lãi cho năm tiếp theo.
Choose the right answer Sacagawea was a Shoshone woman who accompanied the first United States expedition to the Pacific Coast. She acted as an interpreter and guide for William Clark and Meriwether Lewis, who were sent to explore the Western United States by President Thomas Jefferson. It is believed that Sacagawea was born in a Shoshone village located near today’s Idaho in 1788. She was kidnapped at age 12 by a tribe called the Hidatsa who lived near today’s North Dakota. When she was 13 years old, she was married to a Canadian trader named Toussaint Charbonneau who was living in the village. During the winter of 1804, Lewis and Clark arrived near the Hidatsa village and built a fort. There, they tried to find people who could help them on their journey. Lewis and Clark decided to hire Charbonneau, knowing that his wife Sacagawea spoke Shoshone. They knew that she could help them when they met the Shoshone later on in their trip. At this time, Sacagawea was pregnant with her first child. She gave birth to a little boy just before embarking on the journey. He would participate in all of the travels and later be adopted by William Clark. Sacagawea was able to reunite with her people during the expedition. When the group reached the Shoshone village, she found that the chief was her long-lost brother. Clark’s journal entry tells of their powerful reunion. Indeed, Clark’s journal hints many times that Sacagawea had a profound effect on the expedition. Clearly, her presence as native guide and as the trip’s only woman was very important to both Lewis and Clark. It is known that she overcame a lot of obstacles and served as a loyal and keen interpreter for Lewis and Clark. In fact, not much is known about Sacagawea except her role in the expedition. There is little hard evidence to support various beliefs about how she lived after the journey and how and when she died. Sacagawea, however, was used as an icon of American feminism in the early 20th century to arouse the sense of self-worth of women. Because of her ability and accomplishments, she is still admired in the United States today. 70. Which title best expresses the main idea of the passage? A. Sacagawea’s Devotion to the Shoshone Tribe B. Early American Feminism in the Sacagawea Legend C. The Life of Sacagawea Shown in William Clark’s Journal D. Sacagawea and Her Role in the Lewis and Clark Expedition 71. In line 2, the word interpreter is closest in meaning to A. doctor B. writer C. mother D. translator 72. Why did Lewis and Clark want a Shoshone-speaking guide? A. They were interested in making a profit from trading. B. They needed someone who had a relationship with the chief. C. They knew they would meet the Shoshone during their travels. D. They wanted to learn the language so the Shoshone would cooperate. 73. The author mentions all of the following EXCEPT A. Sacagawea becoming a mother B. The marriage of Charbonneau and Sacagawea C. Sacagawea reuniting with the Shoshone people D. Thomas Jefferson’s specific goals for the journey 74. What does the author say about Sacagawea’s death? A. It made her a heroine. B. It doesn’t have a clear story. C. It was written about by Clark. D. It occurred while she was running away. 75. In line 12, the word He refers to A. Shoshone chief B. Sacagawea’s son C. Sacagawea’s brother D. Sacagawea’s husband 76. Why does the author mention Sacagawea’s role in 20th-century feminism? A. To discuss Sacagawea’s unique female abilities B. To show that Sacagawea inspired American women C. To explain why Sacagawea is on many American coins D. To remind readers that Sacagawea is only a legend 77. Based on the passage, what is probably true about Lewis and Clark? A. They learned the Shoshone language. B. They never met with Thomas Jefferson. C. They were grateful for Sacagawea’s help. D. They didn’t make it across the United States.
Để trung hòa axit đơn chức A cần 0,2 mol NaOH , đốt A thu được 0,6 mol co2, A phản ứng với brom theo tỉ lệ 1:1. Tìm% khối lượng O trong axit
cho hình chóp S.ABCD có đáy ABCD là hình chữ nhật cạnh AB=a, AD = 2a. mặt phẳng (SAB) và (SAC) vuông góc với ( ABCD).Gọi H là hình chiếu của A lên SD. Tính Khoảng cách giữa AH và SC biết AH = a
Lý lẽ và nghệ thuật lập luuaanj của bài đấu tranh cho một thế giới hòa bình
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