\(\text{Bài 1:}\\ 1)\ (4x+7yz)^2=(4x)^2+2.4x.7yz+(7yz)^2=16x^2+56xyz+49y^2z^2\\ 2)\ (yx^2-3ab)^2=(yx^2)^2-2.yx^2.3ab+(3ab)^2=y^2x^4-6yx^2ab+9a^2b^2\\ 3)\ (x^2-5z)(x^2+5z)=(x^2)^2-(5z)^2=x^4-25z^2\\ 4)\ (2x^2-3)^3=(2x^2)^3-3.(2x^2)^2.3+3.2x^2.3^2-3^3=8x^6-36x^4+54x^2-27\\ 5)\ (a^2+2b^2)^2=(a^2)^2+2.a^2.2b^2+(2b^2)^2=a^4+4a^2b^2+4b^4\\ 6)\ (5xy+2x)^2=(5xy)^2+2.5xy.2x+(2x)^2=25x^2y^2+20x^2y+4x^2\\ 7)\ (3x-2y)^2=(3x)^2-2.3x.2y+(2y)^2=9x^2-12xy+4y^2\\ \text{Bài 2:}\\ 1)\ x^2+6x+9=x^2+2.x.3+3^2=(x+3)^2\\ 2)\ x^2+10x+25=x^2+2.x.5+5^2=(x+5)^2\\ 3)\ 16x^2-16x+4=(4x)^2-2.4x.2+2^2=(4x-2)^2\\ 4)\ x^2+14xy+49y^2=x^2+2.x.7y+(7y)^2=(x+7y)^2\\ \text{Bài 3:}\\ a,\ 25^2-15^2=(25-15).(25+15)=10.40=400\\ b,\ 205^2-95^2=(205-95).(205+95)=110.300=33000\\ c,\ 36^2-14^2=(36-14).(36+14)=22.50=1100\\ d,\ 950^2-850^2=(950-850).(950+850)=100.1800=180000\\ e,\ 1,24^2-2,48.0,24+0,24^2\\ =1,24^2-2.1,24.0,24+0,24^2\\ =(1,24-0,24)^2\\ =1^2=1\)
chúc em học tốt!
