Question

(x-1)^2 - (x+4)^2

Answer 1

`(x-1)^2-(x+4)^2=(x-1-x-4)(x-1+x+4)=-5(2x+3)=-10x-15`

Answer 2

\(\left(x-1\right)^2-\left(x+4\right)^2=\left[\left(x-1\right)-\left(x+4\right)\right]\left[\left(x-1\right)+\left(x+4\right)\right]=\left(x-1-x-4\right)\left(x-1+x+4\right)=-5\times\left(2x-3\right)=-10x+15\)áp dụng hằng đẳng thức \(a^2-b^2=\left(a-b\right)\left(a+b\right)\)