Question

[mai ha phu loc]

TÍNH HỢP LÍ GIÁ TRỊ BIỂU THỨC

A=(-8).25.(-2).4.(-5).125

B=19.25+9.25+19.50

BIẾN ĐỔI VẾ TRÁI THÀNH VẾ PHẢI

(a+b).(a-b)=a^2-b^2

(a+b)^2=a^2+2ab+b^2

xy+x+y+1=(x+1).(y+1)

CHỨNG MINH

(a-b)-(c-d)=(a+d)-(b+c)

MK ĐANG CẦN RẤT RẤT  GẤP 

AI LÀM NHANH MK TIK CHO

-))) THANK YOU SO MUCH

Answer 1

[Lam Ngo Tung]

\(A=\left(-8\right).25.\left(-2\right).4.\left(-5\right).125\)

   \(=\left(-8\right).\left(-125\right).25.4.\left(-2\right).\left(-5\right)\)

   \(=1000.100.10\)

   \(=1000000\)

Vay \(A=1000000\)

\(B=19.25+9.25+19.50\)

    \(=25.\left(19+9\right)+19.50\)

    \(=25.28+19.50\)

    \(=50.14+19.50\)

    \(=50.\left(14+19\right)\)

    \(=50.33\)

    \(=1650\)

Vay \(B=1650\)

a) Ta co :

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

\(\RightarrowĐPCM\)

b) Ta co :

 \(a^2+2ab+b^2=a\left(a+b\right)+b\left(a+b\right)=\left(a+b\right)\left(a+b\right)=\left(a+b\right)^2\)

\(\RightarrowĐPCM\)

c) Ta co :

\(\left(x+1\right)\left(y+1\right)=xy+x+y+1\)

\(\RightarrowĐPCM\)

d) Ta có : 

\(\left(a-b\right)-\left(c-d\right)=a-b-c+d=\left(a+d\right)-\left(b+c\right)\)

\(\RightarrowĐPCM\)