a)\(69^2-31^2=\left(69-31\right)\left(69+31\right)=38.100=3800\)

\(1023^2-23^2=\left(1023-23\right)\left(1023+23\right)=1000.1046=1046000\)

\(c,\left(27+73\right)^2-2.27.73+54.73\)

\(100^2-54.73+54.73=10000\)

\(d,\left(63-13\right)^2+2.13.63-26.63=50^2=2500\)

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

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

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

b: =20+49-289=20-240=-220

a: =25x100-150=2500-150=2350

c: \(=520:\left\{515\cdot25\right\}\)

=104/2575

1. a) 101² - 99² = (101 + 99)(101 - 99) = 200 . 2 = 400

b) 98.102 = (100 - 2)(100 + 2) = 100² - 4 = 10000 - 4 = 9996

c) 77² + 23² + 77.46 = 77² + 23² + 77.23.2 = (23 + 77)² = 100² = 10000

d) M = x³ + 9x² + 27x + 27 = (x + 3)³ = (7 + 3)³ = 10³ = 1000

2. a) 2x² + 3x - 5 = 0

=> 2x² + 5x - 2x - 5 = 0

=> x(2x + 5) - (2x + 5) = 0

=> (x - 1)(2x + 5) = 0

=> \(\orbr{\begin{cases}x-1=0\\2x+5=0\end{cases}}\)

=> \(\orbr{\begin{cases}x=1\\x=-\frac{5}{2}\end{cases}}\)

b) 2x² - 11x - 51 = 0

=> 2x² - 17x + 6x - 51 = 0

=> x(2x - 17) + 3(2x - 17) = 0

=> (x + 3)(2x - 17) = 0

=> \(\orbr{\begin{cases}x+3=0\\2x-17=0\end{cases}}\)

=> \(\orbr{\begin{cases}x=-3\\x=\frac{17}{2}\end{cases}}\)

a) 101² - 99² = (101-99)(101+99)= 2,200 = 4002

b)98.102 = (100-2)(100+2) = 100² - 2² =10000 - 4 = 9996

c) 77² + 23² +77.46 = 77² + 23² +2.77.23 = ( 77+23)² = 100² =1000

d) Với x=7 => M = 7³+ 9.7³ + 27.7 + 27 = 10.7³ +27.8 = 10.343 + 216 = 3430+216 = 3646

2. a) 2x² + 3x -5 =0

=> 2(x² +3/2 x +9/16) -49/8 = 0

=> 2 (x+3/4)² =49/8

=> (x+3/4)² =49/16 = (7/4)² = (-7/4)²

=> x+3/4 = 7/4 hoặc x+3/4 = -7/4

=> x= 1 hoặc x=-5/2

b) 2x² -11x - 51 =0

=> 2(x² -11/2x + 121/16) -529/8 = 0

=> (x -11/4)² = 529/16 = (23/4)² =(-23/4)²

=> x-11/4=23/4 hoặc x-11/4 = -23/4

=> x=17/2 hoặc x=-3

giúp mk câu này nx 

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