Question

X square 2 + 4 x minus 21 is equal to zero

Answer 1

Step-by-step explanation:

$\tt \red{ \leadsto \: x {}^{2} + 4x - 21 = 0}$

$\tt \pink{ \leadsto \: a+b=4 \qquad \qquad \leadsto ab=1\left(-21\right)=-21 }$

$\tt \blue{ \leadsto-1,21 \qquad \qquad \leadsto-3,7 }$

$\tt \orange{ \leadsto \: a=-3 \qquad \qquad \leadsto \: b=7 }$

$\tt \purple{ \leadsto\left(x^{2}-3x\right)+\left(7x-21\right) }$

$\tt \green{ \leadsto \: x\left(x-3\right)+7\left(x-3\right) }$

$\tt \orange{ \leadsto\left(x-3\right)\left(x+7\right) }$

$\tt \red{ \leadsto\left(x-3\right) = 0 \quad \: and \quad\left(x+7\right) = 0}$

$\tt \pink{ \leadsto \: x = 3 \quad \: and \quad \: x = - 7}$