Question

$a) x^{2} +5x - 14 = 0 , b) x^{2} - 4x -21 = 0,c) x^{2} + 6x - 40 =0$

Answer 1

[tex]a)x^2+5x-14=0 \\ x^2+7x-2x-14=0 \\ x(x+7)-2(x+7)=0 \\ (x+7)(x-2)=0\\ S:x\in \{2;-7 \}\\ \\ b)x^2-4x-21=0 \\ x^2-7x+3x-21=0\\ x(x-7)+3(x-7)=0\\ (x-7)(x+3)=0\\ S:x\in \{7;-3\}\\ \\ c)x^2+6x-40=0 \\ x^2+10x-4x-40 =0 \\ x(x+10)-4(x+10)=0\\ (x+10)(x-4)=0\\ S:x\in \{-10;4\}[/tex]