Question

разложите на множители
$(a - 2)^{2} + 4(a - 2) - 21$

Answer 1

$(a - 2) {}^{2} + 7(a - 2) - 3(a - 2) - 21 = \ \ (a - 2)(a - 2 + 7) - 3( a - 2 + 7) = \ \ (a - 2 + 7)(a - 2 - 3) = \ \ (a + 5)(a - 5)$

Answer 2

$x^2+4x-21=0; ; to ; ; x_1=-7; ,; x_2=3; ; (teorema; Vieta); ; Rightarrow \\x^2+4x-21=(x+7)(x-3); ; ; Rightarrow \\x=(a-2), :; (a-2)^2+4(a-2)-21=(a-2+7)(a-2-3)=(a+5)(a-5)$