Đáp án:
Giải thích các bước giải:
Bài 1:
a) (x-3)^2
= x^2 -2.x.3 +3^2
= x^2 -6x +9
b) (x- 1/2)^2
= x^2 - 2.1/2.x + (1/2)^2
= x^2 -x +1/4
c) (5x -y)^2
= (5x)^2 - 2.5x.y +y^2
= 25x^2 -10xy +y^2
d) (10x^2 -3xy^2 )^2
= (10x^2) ^2 - 2.10x^2 .3xy^2 +(3xy^2)^2
= 100x^4 - 60 x^2 .y^2 +9x^2 .y^4
Bài 2:
a) x^2 -4x+4
= x^2 - 2.2.x +2^2
= (x-2)^2
b) x^2 -10x +25
= x^2 -2.x.5 +5^2
= (x-5)^2
c) x^2 /4 -x +1
= (x/2)^2 - 2.x/2 +1^2
= (x/2 -1)^2
d) 9(x+1)^2 -6(x+1) +1
= 9(x^2 +2x +1) - 6(x+1) +1
= 9x^2 +18x +9 - 6x -6 +1
= 9x^2 + (18x-6x) +(9-6+1)
= 9x^2 +12x + 4
= (3x)^2 +2.3x.2 + 2^2
= (3x+2)^2
e) (x-2y)^2 -8(x^2 -2xy) +16x^2
= x^2 -2.x.2y + (2y)^2 - 8x^2 -8.(-2xy) +16x^2
= x^2 - 4xy +4y^2 -8x^2 +16xy +16x^2
= (x^2 -8x^2 +16x^2) + (-4xy +16xy) +4y^2
= 9x^2 +12xy +4y^2
= (3x)^2 + 2.3x.2y + (2y)^2
= (3x+ 2y)^2
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