\(B=5\cdot\left(2x-1\right)^2+4\cdot\left(x-1\right)\cdot\left(x+3\right)-2\cdot\left(5\cdot3x\right)\)
\(=5\left(4x^2-4x+1\right)+\left(4x-4\right)\cdot\left(x+3\right)-2\cdot15x\)
\(=20x^2-20x+5+4x^2+12x-4x-12-2\cdot15x\)
\(=20x^2-20x+5+4x^2+12x-4x+12-30x\)
\(=24x^2-42x-7\)
(B=5left(2x-1 ight)^2+4left(x-1 ight)left(x+3 ight)-2left(5.3x ight)=5left(4x^2-4x+1 ight)+4left(x^2-4x+3 ight)-30x=20x^2-20x+5+4x^2-16x+12-30x=24x^2-66x+17)
\(B=5.\left(2x-1\right)^2+4\left(x-1\right)\left(x+3\right)-2\left(5.3x\right)\)
\(B=5\left(4x^2-4x-1\right)+4\left(x^2+3x-x-3\right)-30x\)
\(B=20x^2-20x-5+4x^2+8x-12-30x\)
\(B=24x^2-2x-17\)
Chúc bạn học tốt!!!
