Question

tính

a)\(101^2-99^2\)

b)98.102

c)\(77^2+23^2+77.46\)

d)M=\(x^3+9x^2+27x+27\)tại x=7

TÌM X

a)\(2x^2+3x-5=0\)

b)\(2x^2-11x-51=0\)

AI GIÚP MK VS MAI MK KIỂM TRAI RÙI 

Answer 1

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

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

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

Answer 2

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

Answer 3

giúp mk câu này nx 

\(\left(3x^2y^2+6x^2y^3-12xy\right)\):3xy

Answer 4

(3x²y² +6x²y³ - 12xy) : 3xy

= 3x²y² : 3xy + 6x²y³ : 3xy -12xy :3xy

= xy +2xy² -4