Write an octonion x {\displaystyle x} in the form x = ( a + v ) + ℓ ( b + w ) {\displaystyle x=(a+\mathbf {v} )+\ell (b+\mathbf {w} )} where a {\displaystyle a} and b {\displaystyle b} are real numbers and v and w are pure imaginary quaternions regarded as vectors in R3. Écrivons un octonion x sous la forme x = ( a + a ) + ℓ ( b + b )
