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I) Hình bạn tự vẽ nha
Ta có DY//BH ; YH//DB
=> DYHB hình bình hành => DY = HB
Tương tự được ZE = FC
mà \(\frac{BH}{BC}=1-\frac{HC}{BC}=1-\frac{1}{\sqrt{2}}\)\(\left(\Delta HIC\approx\Delta BAC;\frac{AB}{IH}=\sqrt{2}\right)\)(1)
Tương tự được \(\frac{FC}{BC}=1-\frac{BF}{BC}=1-\frac{1}{\sqrt{2}}\)(2)
Từ (1) ; (2) => BH = FC hay DY = ZE
is .............
câu 9.Let ABCD be a trapezoid with bases AB, CD and O be the intersection of AC and BD. If the areas of triangle OAB, triangle OCD are 16cm2, 40cm2respectively and M is the midpoint of BD, then the area of the triangle AMD is .........cm2.
câu 10.Bottle A contains 15% syrup. Bottle B contains 40% syrup. When these 2 bottles of syrup are mixed, the syrup content is 30% and the total volume is 600ml. How much syrup is in the bottle A at first?
câu 11.Let ABCD.A'B'C'D' be a cube with AC' = √3cm. Find the total surface area of this cube.
câu 12.Let ABC be a triangle with AB = 3cm, AC = 7cm. The internal bisector of the angle BAC intersects BC at D. The line passing through D and parallel to AC cuts AB at E. Find the measure of DE.
câu 12.Given two numbers x, y such that (4y2 - 12y + 25)(4x2 + 6x + 4) = 28
câu 16.
ô hello ZT
ét o ét, cần giúp