Bài 8-10 2h đi hc rồi giúp pé đi các thần đồnggg

Đáp án:

 `↓`

Giải thích các bước giải:

Bài `8` : 

`a) 52^2 + 96.52+48^2`

`= 52^2 +2.48.52+48^2`

`= (52+48)^2`

`= 100^2`

`=10000`

`b) 7^4 .2^4 -(14^2 +1)(14^2 -1)`

`= (7.2)^4 - [(14^2)^2 -1^2]`

`= 14^4 - 14^4 + 1`

`=1`

`c) 67^2 + 73^2 - 17^2 - 23^2`

`= (67^7 - 23^2) + (73^2 - 17^2)`

`= (67-23)(67+23)+(73-17)(73+17)`

`= 44.90 + 56.90`

`= (44+56).90`

`= 100.90`

`=9000`

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Bài `9` : 

`a)4x^2 -6x = 2x(2x-3)`

`b) 9x^4y^3 + 3x^2y^4 = 3x^2y^3 (3x^2 +y)`

`c)3x(x-1)+5(x-1)=(x-1)(3x+5)`

`d)(x-3)(x-1)-3(x-3)=(x-3)(x-1-3)=(x-3)(x-4)`

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Bài `10` : 

`a) 4x^2 - 12x+9`

`= (2x)^2 -2.2x.3+3^2`

`= (2x-3)^2`

`b) 9x^2 - 24xy+16y^2`

`=(3x)^2 -2.3x.4y+(4y)^2`

`= (3x-4y)^2`

`c) (2x+5)^2 - (x-9)^2`

`= [2x+5-(x-9)][2x+5+(x-9)]`

`= (2x-x+5+9)(2x+x+5-9)`

`= (x+14)(3x-4)`

`d) 1+8x^6y^3`

`= 1^3 +(2x^2y)^3`

`=(1+2x^2y)[1^2 -1.2x^2y+(2x^2y)^2]`

`= (1+2x^2y)(1-2x^2y+4x^4y^2)`

`e) 27x^3 + (y^3)/8`

`= (3x)^3 + (y/2)^3`

`= (3x+ y/2)[(3x)^2 - 3x . y/2 +(y/2)^2]`

`= (3x + y/2)(9x^2 - 3/3 xy + (y^2)/4)`

`g)(4x^2 - 25)^2 - 9(2x-5)^2`

`= (4x^2 - 25)^2 - 3^2 .(2x-5)^2`

`=  (4x^2 - 25)^2 -[3(2x-5)]^2`

`= (4x^2 - 25)^2 -(6x-15)^2`

`=(4x^2 -25+6x-15)(4x^2 - 25-6x+15)`

`= (4x^2 + 6x - 40)(4x^2 - 6x - 10)`

`= 2(2x^2 + 3x-20).2(2x^2 - 3x-20)`

`= 4(2x^2 + 3x-20)(2x^2 - 3x-20)`

`=4(2x^2 -5x+8x-20)(2x^2 + 5x-8x-20)`

`= 4[x(2x-5)+4(2x-5)][x(2x+5)-4(2x+5)]`

`= 4(x+4)(2x-5)(x-4)(2x +5)`

`= 4(x^2 -4^2)[(2x)^2 -5^2]`

`= 4(x^2 -16)(4x^2 - 25)`