Question

How to solve it ...

1. 5-2x²-6x
2. (x+3) (x+4)=0

Answer 1

`1.\\5-2x^2-6x=0\\-2x^2-6x+5=0\\\\a=-2;\ b=-6;\ c=5\\\\\Delta=b^2-4ac\to\Delta=(-6)^2-4\cdot(-2)\cdot5=36+40=76\\\\x_1=(-b-\sqrt\Delta)/(2a)\to x_1=(6-√(78))/(2\cdot(-2))=(6-√(4\cdot19))/(-4)=(6-2√(19))/(-4)=(√(19)-3)/(2)\\\\x_2=(-b+\sqrt\Delta)/(2a)\to x_2=(3-√(19))/(2)`

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`2.\\(x+3)(x+4)=0\iff x+3=0\ \vee\ x+4=0\\\\x=-3\ \vee\ x=-4`