\(a)37,5.8,5-7,5.3,4-6,6.7,5+1,5.37,5\)

\(=\left(37,5.8,5+1,5.37,5\right)-\left(7,5.3,4+6,6.7,5\right)\)

\(=37,5\left(8,5+1,5\right)-7,5\left(3,4+6,6\right)\)

\(=37,5.10-7,5.10\)

\(=10\left(37,5-7,5\right)\)

\(=10.30\)

\(=300\)

\(b)35^2+40^2-25^2+80.35\)

\(=\left(35^2+80.35+40^2\right)-25^2\)

\(=\left(35+40\right)^2-25^2\)

\(=75^2-25^2\)

\(=\left(75-25\right)\left(75+25\right)\)

\(=50.100\)

\(=5000.\)

3a² - 6ab + 3b² - 12c²

a)\(37,5\times8,5+-7,5\times3,4-6,6\times7,5+1,5\times37,5\)

\(=\left(37,5\times8,5+1,5\times37,5\right)-\left(7,5\times3,4+6,6\times7,5\right)\)

\(=37,5\left(8,5+1,5\right)-7,5\left(3,4+6,6\right)\)

\(=375-75\)

\(=300\)

phần a) bn chép sai phải ko?

số 85 ý

a) 37,5.8,5 - 7,5.3,4 - 6,6.7,5 + 1,5.37,5

= (37,5.8,5 + 1,5.37,5) - (7,5.3,4 + 6,6.7,5)

= 37,5(8,5 + 1,5) - 7,5(3,4 + 6,6)

=37,5.10 - 7,5.10

=375 - 75

= 300

b) 35² + 40² - 25² + 80.35

= (35² + 80.35 + 40²) - 25²

= (35 + 40)² - 25²

= (35 + 40 - 25)(35 + 40 + 25)

= 50.100

= 5000

a) 37,5.8,5-7,5.3,4-6,6.7,5+1,5.37,5

=(37,5.8,5+1,5.37,5)-(7,5.3,4+6,6.7,5)

=37,5.(8,5+1,5)-7,5.(3,4+6,6)

=37,5.10-7,5.10

=375-75

=300

b) 35²+40²-25²+80.35

=(35²+80.35+40²)-25²

=(35+40)²-25²

=(35+40+25).(35+40-25)

=100.50

=5000

\(37,5.8,5-7,5.3,4-6,6.7,5+1,5.37,5\)

\(=\left(37,5.8,5+1,5.37,5\right)-\left(7,5.3,4+6,6.7,5\right)\)

\(=37,5\left(8,5+1,5\right)-7,5\left(3,4+6,6\right)\)

\(=37,5.10-7,5.10\)

\(=10\left(37,5-7,5\right)\)

\(=10.30\)

\(=300\)

\(37,5.8,5-7,5.3,4-6,6.7,5+1,5.37,5\)

\(=\left(37,5.8,5+1,5.3,5\right)+\left(-7,5.3,4-6,6.7,5\right)\)

\(=37,5\left(8,5+1,5\right)-7,5\left(3,4+6,6\right)\)

\(=37,5.10-7,5.10\)

\(=10.\left(37,5-7,5\right)\)

\(=10.30=300\)

a) Cậu hình như chép thiếu đề

b) \(35^2+40^2-25^2+80.35\)

= 35² +2.40.35 +40² -25²

= (35 +40)² - 25²

= ( 35+40-25).(35+40+25)

=100.50

=5000

Bài 1:

a) \(x^2-y^2-2yz-z^2\)

\(=x^2-\left(y^2+2yz+z^2\right)\)

\(=x^2-\left(y+z\right)^2\)

\(=\left(x+y+z\right)\left(x-y-z\right)\)

b) \(2xy-x^2-y^2+16\)

\(=16-\left(x^2-2xy+y^2\right)\)

\(=4^2-\left(x-y\right)^2\)

\(=\left(4+x-y\right)\left(4-x+y\right)\)

c) \(3a^2-6ab+3b^2-12c^2\)

\(=3\left(a^2-2ab+b^2-4c^2\right)\)

\(=3\left[\left(a^2-2ab+b^2\right)-\left(2c\right)^2\right]\)

\(=3\left[\left(a-b\right)^2-\left(2c\right)^2\right]\)

\(=3\left(a-b-2c\right)\left(a-b+2c\right)\)

Bài 2:

a) \(37,5\cdot8,5-7,5\cdot3,4+6,6\cdot7,5+1,5\cdot37,5\)

\(=\left(37,5\cdot8,5+1,5\cdot37,5\right)-\left(7,5\cdot3,4-6,6\cdot7,5\right)\)

\(=37,5\cdot\left(8,5+1,5\right)-7,5\cdot\left(3,4-6,6\right)\)

\(=37,5\cdot10-7,5\cdot10\) (mk đoán đề bạn chép sai)

\(=10\cdot\left(37,5-7,5\right)\)

\(=10\cdot30\)

\(=300\)

b) \(35^2+40^2-25^2+80\cdot35\)

\(=\left(40^2+2\cdot40\cdot35+35^2\right)-25^2\)

\(=\left(40+35\right)^2-25^2\)

\(=75^2-25^2\)

\(=\left(75+25\right)\left(75-25\right)\)

\(=100\cdot50\)

\(=5000\)

Bài 1:

a, \(x^2-y^2-2yz-z^2=x^2-\left(y^2+2yz+z^2\right)\)

\(=x^2-\left(y+z\right)^2=\left(x-y-z\right)\left(x+y+z\right)\)

b, \(2xy-x^2-y^2+16=16-\left(x^2-2xy+y^2\right)\)

\(=16-\left(x-y\right)^2=\left(4-x+y\right)\left(4+x-y\right)\)

c, \(3a^2-6ab+3b^2-12c^2\)

\(=3\left(a-b\right)^2-12c^2=3\left[\left(a-b\right)^2-4c^2\right]\)

\(=3\left(a-b+2c\right)\left(a-b-2c\right)\)

Bài 2:

a, \(37,5.8,5-7,5.3,4+6,6.7,5+1,5.37,5\)

\(=37,5.\left(8,5+1,5\right)-7,5.\left(3,4+6,6\right)\)

\(=37,5.10-7,5.10=10.\left(37,5-7,5\right)\)

\(=10.30=300\)

b, \(35^2+40^2-25^2+80.35\)

\(=\left(40^2+2.40.35+35^2\right)-25^2\)

\(=\left(40+35\right)^2-25^2=75^2-25^2\)

\(=\left(75-25\right)\left(75+25\right)=50.100=5000\)

https://hoc24.vn//hoi-dap/question/447059.html

Bài giải:

a) 37,5 . 6,5 – 7,5 . 3,4 – 6,6 . 7,5 + 3,5 . 37,5

= (37,5 . 6,5 + 3,5 . 37,5) - (7,5 . 3,4 + 6,6 . 7,5)

= 37,5(6,5 + 3,5) - 7,5(3,4 + 6,6)

= 37,5 . 10 - 7,5 . 10

= 375 - 75 = 300.

b) 45² + 40² – 15² + 80 . 45 = 45² +2 . 40 . 45 + 40² – 15²

= (40 + 45)² – 15² = 85² – 15² = (85 – 15)(85 + 15) = 70 . 100 = 7000.

a) 37,5.6,5-7,5.3,4-6,6.7,5+3,5.37,5

=(37,5.6,5+3,5.37,5)-(7,5.3,4+6,6.7,5)

=37,5.(6,5+3,5)-7,5.(3,4+6,6)

=37,5.10-7,5.10

=375-75

=300

b) 45²+40²-15²+80.45

=45²+2.40.45+40²-15²

=(45+40)²-15²

=(45+40-15).(45+40+15)

= 70.100

=7000

a) 37,5 . 6,5 - 7,5 . 3,4 - 6,6 . 7,5 + 3,5 . 37,5

= 37,5 . 6,5 + 3,5 . 37,5 - 7,5 . 3,4 - 6,6 .7,5

= 37,5 (6,5 + 3,5) - 7,5 (3,4 + 6,6)

= 37,5 . 10 - 7,5 . 10

= 375 - 75 = 300

b) 45² + 40² - 15² + 80 . 45

= 45² + 80 . 45 + 40² - 15²

= 45² + 2 . 40 .45 + 40² - 15²

= (45 + 40)² - 15²

= 85² - 15²

= (85 + 15) (85 - 15)

= 100 . 70 = 7000

\(a,2x^2-2xt-5x+5y\)

\(=\left(2x^2-5x\right)-\left(2xy-5y\right)\)

\(=x\left(2x-5\right)-y\left(2x-5\right)\)

\(=\left(2x-5\right)\left(x-y\right)\)

\(b,8x^2+4xy-2ax-ay\)

\(=\left(8x^2-2ax\right)+\left(4xy-ay\right)\)

\(=2x\left(4x-a\right)+y\left(4x-a\right)\)

\(=\left(4x-a\right)\left(2x+y\right)\)

\(c,x^3-4x^2+4x\)

\(=x^3-2x^2-2x^2+4x\)

\(=\left(x^3-2x^2\right)-\left(2x^2-4x\right)\)

\(=x^2\left(x-2\right)-2x\left(x-2\right)\)

\(=\left(x-2\right)\left(x^2-2x\right)=x\left(x-2\right)\left(x-2\right)\)

\(=x\left(x-2\right)^2\)

\(d,2xy-x^2-y^2+16\)

\(=-\left(x^2-2xy+y^2-16\right)\)

\(=-\left[\left(x-y\right)^2-4^2\right]\)

\(=-\left(x-y-4\right)\left(x-y+4\right)\)

\(e,x^2-y^2-2yz-z^2\)

\(=x^2-\left(y^2+2yz+z^2\right)\)

\(=x^2-\left(y+z\right)^2=\left(x-y-z\right)\left(x+y+z\right)\)

bài 3

a) 37,5 . 8,5-7,5.3,4-6,6.7,5 +1,5.37,5

=(37,5.8,5+1,5.37,5)-(7,5 .3,4+6,6.7,5)

=37,5(8,5+1,5)-7,5(3,4+6,6

=37,5.10-7,5.10

=10(37,5-7,5)

=10.30

=300

b)35²+40²-25²+80.35

=35²+2.40.35+40²-25²

=(35²+2,40.35+40²)-25²

=(35+40)² -25²

=(35+40-25)(35+40+25)

=50.100

5000