Question

2c) * tính (2x-y2)^2b

* tính nhanh 999²

3.a) vơí a,b là hai số bất kì,tính (a+b)(a-b)

c) *tính (x-2y)(x+2y) theo mẫu (trang 13 - VNEN)

* tính nhanh 77.83 theo mẫu (trang 14 - sách VNEN)

Answer 1

2c) * \(\left(2x-2y\right)^{2b}\)

\(=\left(2x\right)^{2b}-2\cdot2x\cdot2y+\left(2y\right)^{2b}\)

* \(999^2\)

\(=\left(1000-1\right)^2\)

\(=1000^2-2\cdot1000\cdot1+1^2\)

\(=998001\)

3a) * \(\left(a+b\right)\left(a-b\right)=a^2-b^2\)

* \(\left(x-2y\right)\left(x+2y\right)=x^2-4y^2\)

* \(77\cdot83\)

\(=\left(70-3\right)\left(70+3\right)\)

\(=70^2-3^2\)

\(=3991\)

Answer 2

2c)

\(\left(2x-2y\right)^{2b}=\left(2x\right)^{2b}-8xy+\left(2y\right)^{2b}\)

Tính nhanh:\(999^2=\left(1000-1\right)^2=1000^2-2.1000.1+1^2=998001\)

Answer 3

3a)\(\left(a+b\right)\left(a-b\right)=a^2-b^2\)

c)\(77.83=\left(80-3\right)\left(80+3\right)=80^2-3^2=6391\)