Question

I really need help quick

y = x² -4x

find values of x when y=2

with explanation please

Answer 1

`\sf x=2+√(6),\:x=2-√(6)`

Step-by-step explanation:

`\sf y = x^2 -4x`

given that y = 2

`\sf x^2 -4x = 2`

`\sf x^2 -4x -2 = 0`

using quadratic formula:

`\sf x = ( -b \pm √(b^2 - 4ac))/(2a) \ \ \ when \ ax^2 + bx + c = 0`

`\rightarrow \sf x_(1,\:2)=(-\left(-4\right)\pm √(\left(-4\right)^2-4\cdot \:1\cdot \left(-2\right)))/(2\cdot \:1)`

`\rightarrow \sf x_1=(-\left(-4\right)+2√(6))/(2\cdot \:1),\:x_2=(-\left(-4\right)-2√(6))/(2\cdot \:1)`

`\rightarrow \sf x=2+√(6),\:x=2-√(6)`

in decimals:

`\rightarrow \sf x=4.45 , \ -0.45`