Ok i really need

so i had a test and i had to find the area of a triangle so i did,

,isn't that the formula for triangles?
but my teacher marked it wrong and i don't know why
pl i need to know what i did wrong and my teacher isn't available.
is there a different formula for this type of triangle?

for a normal triangle its (bh)/2 but this is a right triangle so you multiply the two perpendicular sides and divide it by 2

47

step-by-step explanation:

let's call the solutions x₁ = (5 - 2√7)/3 and x₂ = (5 + 2√7)/3

then the equation is (x-x₁)(x-x₂) = 0

if you fill that in you get a lot of numbers which you can recognize as ax²+bx+c=0.

step-by-step explanation:

you can see that a=1 (there is just an x²)

b = (-5 -2√7 + 2√7 - 5)/3 = -10/3

c = -2√7)/3 ) * (-5+2√7)/3) = -1/3

so your answer is 3x^2 – 10x – 1 = 0