Câu hỏi của Đinh thủy tiên

Question

Giải hộp mình nha

Bài tập Tất cả

Trần Việt Linh · Accepted Answer

a) $A=\left(2x-1\right)^2+2\left(2x-1\right)\left(3x+1\right)+\left(3x+1\right)^2=\left(2x-1+3x+1\right)^2=\left(5x\right)^2=25x^2$

Thay $x=-\frac{1}{5}$ vào A ta cọ

$A=25\cdot\left(-\frac{1}{5}\right)^2=25\cdot\frac{1}{25}=1$

b)$B=\left(4x-3\right)^2-2\left(16x^2-9\right)+\left(4x+3\right)^2$

$=\left(4x-3\right)^2-2\left(4x-3\right)\left(4x+3\right)+\left(4x+3\right)^2=\left(4x-3-4x-3\right)^2=-6^2$

Vói x=-17 thì $B=\left(-6\right)^2=36$

Câu trả lời:

a) $A=\left(2x-1\right)^2+2\left(2x-1\right)\left(3x+1\right)+\left(3x+1\right)^2=\left(2x-1+3x+1\right)^2=\left(5x\right)^2=25x^2$

Thay $x=-\frac{1}{5}$ vào A ta cọ

$A=25\cdot\left(-\frac{1}{5}\right)^2=25\cdot\frac{1}{25}=1$

b)$B=\left(4x-3\right)^2-2\left(16x^2-9\right)+\left(4x+3\right)^2$

$=\left(4x-3\right)^2-2\left(4x-3\right)\left(4x+3\right)+\left(4x+3\right)^2=\left(4x-3-4x-3\right)^2=-6^2$

Vói x=-17 thì $B=\left(-6\right)^2=36$

Edowa Conan · Answer

A=(2x-1)²+2.(2x-1)(3x-1)+(3x+1)²

A=4x²-4x+1+2.(6x²-5x+1)+9x²+6x+1

A=13x²+2x+2+12x²-10x+2

A=25x²-8x+4

A=(5x)²-2.4x+2²

A=(5x-2)² Tại x=$-\frac{1}{5}$ ta có:

A=(5x-2)²

A=$\left[5.\left(-\frac{1}{5}\right)-2\right]^2$

A=$\left(-1-1\right)^2$

A=(-2)²=4

b)B=(4x-3)²-2.(16x²-9)+(4x+3)²

B=16x²-24x+3²-32x²+18+16x²+24x+3²

B=3²+3²+18

B=36