Question

cho a,b,c thỏa mãn a²=b²+c² và b²=2c²-2013.tính giá trị của biểu thức:

Q=5a²-7b²-c²

Answer 1

Ta có

\(a^2=2c^2-2013+c^2=3c^2-2013\)

\(\Rightarrow Q=5\left(3c^2-2013\right)-7\left(2c^2-2013\right)-c^2=15c^2-10065-14c^2+14091-c^2=4026\)

Answer 2

Thay b^2=2c^2-2013, ta co: a^2=2c^2-2013+c^2=3c^2-2013 => 5a^2=15c^2-10065

7b^2=7(2c^2-2013)=14c^2-14091

Suy ra Q=15c^2-10065-14c^2+14091-c^2=4026

Answer 3

24102005

Answer 4

(ab+ac+bc)2=49" role="presentation" style="border:0px; direction:ltr; display:inline-block; float:none; font-size:16.38px; line-height:0; margin:0px; max-height:none; max-width:none; min-height:0px; min-width:0px; padding:1px 0px; position:relative; white-space:nowrap; word-spacing:normal; word-wrap:normal" class="MathJax_CHTML mjx-chtml">(ab+ac+bc)2=49

(ab)2+(bc)2+(ac)2=49" role="presentation" style="border:0px; direction:ltr; display:inline-block; float:none; font-size:16.38px; line-height:0; margin:0px; max-height:none; max-width:none; min-height:0px; min-width:0px; padding:1px 0px; position:relative; white-space:nowrap; word-spacing:normal; word-wrap:normal" class="MathJax_CHTML mjx-chtml">(ab)2+(bc)2+(ac)2=49

a4+b4+c4=(a2+b2+c2)2−2(ab)2−2(ac)2−2(bc)2=" role="presentation" style="border:0px; direction:ltr; display:inline-table; float:none; font-size:16.38px; line-height:0; margin:0px; max-height:none; max-width:none; min-height:0px; min-width:0px; padding:1px 0px; position:relative; white-space:nowrap; word-spacing:normal; word-wrap:normal" class="MathJax_CHTML mjx-chtml">a4+b4+c4=(a2+b2+c2)2−2(ab)2−2(ac)2−2(bc)2==98

"Thành công lớn nhất là đứng dậy sau những vấp ngã"  Chúc Học Tốt

Answer 5

24102005