Toán Lớp 8: Giải hộ mình với ạಥ‿ಥ Bài 1: Khai triển 1) (5+2x)^2 2) (3x-2y)^2 3) (2x+3y^2)^2 4) (x+3)^2-(x-3)^2 Bài 2: Rút gọn 1) (2x+1^2)^2+(x+1)^2

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Toán Lớp 8:  Giải hộ mình với ạಥ‿ಥ Bài 1: Khai triển 1) (5+2x)^2 2) (3x-2y)^2 3) (2x+3y^2)^2 4) (x+3)^2-(x-3)^2 Bài 2: Rút gọn 1) (2x+1^2)^2+(x+1)^2+2(1+3x)+(1-3x) Cảm ơn nhiều ạ(◍•ᴗ•◍)

thanhtung · Answer

Giải đáp:    B&agrave;i 1:   1, (5 + 2x)^2 = 5^2 + 2.5.2x + (2x)^2                         = 25 + 20x + 4x^2   2, (3x - 2y)^2 = (3x)^2 - 2.3x.2y + (2y)^2                         = 9x^2 - 12xy + 4y^2   3, (2x + 3y^2)^2 = (2x)^2 + 2.2x.3y^2 + (3y^2)^2                               = 4x^2 + 12xy^2 + 9y^4   4, (x + 3)^2 - (x - 3)^2   = [(x + 3) + (x - 3)][(x + 3 - (x - 3)]   = (x + 3 + x - 3)(x + 3 - x + 3)   = 2x.6 = 12x   B&agrave;i 2:   1, (2x + 1^2)^2 + (x + 1)^2 + 2(1 + 3x) + (1 - 3x)   = (2x)^2 + 2.2x.1 + 1^2 + x^2 + 2.x.1 + 1^2 + 2.1 + 2.3x + 1 - 3x   = 4x^2 + 4x + 1 + x^2 + 2x + 1 + 2 + 6x + 1 - 3x   = (4x^2 + x^2) + (4x + 2x + 6x - 3x) + (1 + 1 + 2 + 1)   = 5x^2 + 9x + 5   Học tốt

lanminhngoc · Answer

B&agrave;i 1:    1)(5+2x)&sup2;   =5&sup2;+2.5.2x+(2x)&sup2;   =25+20x+4x&sup2;   &Aacute;p dụng HĐT:(A+B)&sup2;=A&sup2;+2AB+B&sup2;   2)(3x-2y)&sup2;   =(3x)&sup2;-2.3x.2y+(2y)&sup2;   =9x&sup2;-12xy+4y&sup2;   &Aacute;p dụng HĐT:(A-B)&sup2;=A&sup2;-2AB+B&sup2;   3)(2x+3y^2)^2   =(2x)^2+2.2x.3y&sup2;+(3y^2)^2   =4x&sup2;+12xy&sup2;+9y^4   &Aacute;p dụng HĐT:(A+B)&sup2;=A&sup2;+2AB+B&sup2;   4)(x+3)&sup2;-(x-3)&sup2;   =[(x+3)+(x-3)][(x+3)-(x-3)]   =(x+3+x-3)(x+3-x+3)   =2x.6   =12x   &Aacute;p dụng HĐT:A&sup2;-B&sup2;=(A+B)(A-B)    B&agrave;i 2:    1)(2x+1^2)^2+(x+1)&sup2;+2(1+3x)+(1-3x)   =(2x)&sup2;+2.2x.1&sup2;+(1^2)^2+x&sup2;+2.x.1+1&sup2;+2+6x+1-3x   =4x&sup2;+4x+1+x&sup2;+2x+1+2+6x+1-3x   =(4x&sup2;+x&sup2;)+(4x+2x+6x-3x)+(1+1+2+1)   =5x&sup2;+9x+5   &Aacute;p dụng HĐT:(A+B)&sup2;=A&sup2;+2AB+B&sup2;