a) A=(2X^2+XY)+(4X+2Y)

      =X(2X+Y) + 2(2X+Y)   

      = (2X+Y)(2+X) 

Thay X=88,Y=-76 

A=(2*88-76)(2+88)=100*90=9000

b) nhóm X^2 với -7X,XY với -7Y,làm tương tự thì B=6

Cảm ơn bạn nhé

\(38^2+76\cdot12+12^2\)

\(=38^2+2\cdot38\cdot12+12^2\)

\(=\left(38+12\right)^2\)

\(=50^2\)

\(=2500\)

=1444+76x12+144

=1444+912+144

=2356+144

=2500

như này đúng ko

a. \(76^2-24^2=\left(76+24\right)\left(76-24\right)=100.52=5200\)

b. \(106^2+106.12+6^2=\left(106+6\right)^2=12544\)

B1:

\(a.301^2=\left(300+1\right)^2=300^2+2.300.1+1^2\\ =90000+600+1=90601\\ b.88^2+2.88.12+12^2=\left(88+12\right)^2=100^2=10000\\ c.99.100=100^2-100=10000-100=9900\\ d,153^2+94.153+47^2=153^2+2.153.47+47^2=\left(153+47\right)^2=200^2=40000\)

B2:

\(A=x^2-20x+101\\ =x^2-2.x.10+10^2+1\\ =\left(x-10\right)^2+1\ge1\forall x\in R\left(Vì:\left(x-10\right)^2\ge0\forall x\in R\right)\\ \Rightarrow min_A=1\Leftrightarrow x-10=0\Leftrightarrow x=10\)

a) \(1,6^2+4.0,8.3,4+3,4^2=1,6^2+2.1,6.3,4+3,4^2=\left(1,6+3,4\right)^2=5^2=25\)

b) \(3^4.5^4-\left(15^2+1\right)\left(15^2-1\right)=15^4-15^4+1=1\)

c) \(76^2+38.48+24^2=76^2+2.38.24+24^2=\left(76+24\right)^2=100^2=10000\)

Câu C pải là 76 ^2 nha bn

Cảm ơn bạn nhaa

`#3107.101107`

`38^2 + 76*12 + 12^2`

`= (38)^2 + 2*38*12 + (12)^2`

`= (38 + 12)^2`

`= 50^2`

`= 2500`

______

Sử dụng hđt:

`(A + B)^2 = A^2 + 2AB + B^2.`

\(38^2+76\cdot12+12^2\)

\(=38^2+2\cdot38\cdot12+12^2\)

\(=\left(38+12\right)^2=50^2=2500\)

\(a.101^2-99^2=\left(101+99\right)\left(101-99\right)=200.2=400\)

\(b.98.102=98.\left(100+2\right)=9800+196=9996\)

\(c,77^2+23^2+77.46=77^2+23^2+2.77.23=\left(77+23\right)^2=100^2=10000\)

a,=(202-54)(202+54)+256*352=248.*256+256*352=256*(248+352)=256*600=256*6*100=153600

b. làm tương tự

c,=5/(1+2+...+10)=5.\(\frac{10.\left(10+1\right)}{2}\)=275

(ta có công thức 1+2+...+n=\(\frac{n.\left(n+1\right)}{2}\) dễ dàng chứng minh)