flycherrypie Group Title solve (x-2)(x+1)=5 step by step please 3 years ago 3 years ago

1. Tomas.A

$(x+2)(x+1)=5$ $x^2+x+2x+2-5=0$ $x^2+3x-3=0$ $D=3\cdot3-4\cdot(-3)\cdot1=21$ $x_{1,2}=\frac{-3\pm\sqrt{21}}{2}$

2. alfie

Anyhow, this is how you do a product... (a+b)(c+d) = a*c+b*d+a*d+b*c.

3. davidmckenna

x * x = x^2 x * 1 = 1x -2 * x = -2x -2 * 1 = -2 Then add them all up and simplify where necessary: x^2-x-7 = 0 Then: x^2-x = 7 And from here I'm stuck aslo :L

4. myininaya

thomas i think there was suppose to be a minus between x and 2 $(x-2)(x+1)=5$ $x^2-2x+x-2=5$ $x^2-x-2-5=0$ $x^2-x-7=0$ $x=\frac{1 \pm \sqrt{1-4(1)(-7)}}{2}$

5. Tomas.A

@myininaya oh yeah sorry, i missed it ><