JEE Main 2022 · 29 Jun · Shift 1 · Mathematics Q3

MathematicsSingle correct+4 / -1Question 3 of 90

If the mirror image of the point $(2,4,7)$ in the plane $3x-y+4z=2$ is $(a,b,c)$ , then $2a+b+2c$ is equal to :

-6

-42

Answer and worked solution

Official answer: C

Image. $t=-\dfrac{2(6-4+28-2)}{26}=-\dfrac{28}{13}$ , giving $\left(-\frac{58}{13},\frac{80}{13},-\frac{21}{13}\right)$ .

Value. $\dfrac{-116+80-42}{13}=-6$ .

(C)

Topics:Angles and distances Equation of a plane

JEE Main 2022 · 29 Jun · Shift 1, Mathematics question 3