( x + 3 )( x + 1 ) = x^2 + 19
x^2 + ( 1 + 3 )x + ( 1 × 3 ) = x^2 + 19
x^2 + 4x + 3 = x^2 + 19
Subtract both sides x^2
x^2 - x^2 + 4x + 3 = x^2 - x^2 + 19
0 + 4x + 3 = 0 + 19
4x + 3 = 19
Subtract both sides 3
4x + 3 - 3 = 19 - 3
4x + 0 = 16
4x = 16
Divide both sides by 4
4x ÷ 4 = 16 ÷ 4
x = 4
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CHECK :
( 4 + 3 )( 4 + 1 ) = 4^2 + 19
( 7 )( 5 ) = 16 + 19
35 = 35
Thus we found the correct value of x which is 4 .
