If $x = 1$ ; $y = 2$ find the values of the following expressions :
(i) $4 x - 3 y + 5$
(ii) $x^{2} + y^{2}$
(iii) $x y + 3 y - 9$

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Solution

Given:
$x = 1, y = 2$
To find the values of given expressions substitute the values of $x$ and $y$ in the expressions.
(i)
$4 x - 3 y + 5 = 4 (1) - 3 (2) + 5 = 4 - 6 + 5 = 3$
$∴ 4 x - 3 y + 5 = 3$ when $x = 1, y = 2$ .
(ii)
$x^{2} + y^{2} = (1)^{2} + (2)^{2} = 1 + 4 = 5$
$∴ x^{2} + y^{2} = 5$ when $x = 1, y = 2$ .

(iii)
$x y + 3 y - 9 = (1) (2) + 3 (2) - 9 = 2 + 6 - 9 = - 1$
$∴ x y + 3 y - 9 = - 1$ when $x = 1, y = 2$ .

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If x=1 ; y=2 find the values of the following expressions :(i) 4x−3y+5 (ii) x2+y2(iii) xy+3y−9

Given: x=1,y=2To find the values of given expressions substitute the values of x and y in the expressions.(i) 4x−3y+5=4(1)−3(2)+5=4−6+5=3 ∴4x−3y+5=3 when x=1,y=2.(ii) x2+y2=(1)2+(2)2=1+4=5∴x2+y2=5 when x=1,y=2.(iii) xy+3y−9=(1)(2)+3(2)−9=2+6−9=−1∴xy+3y−9=−1 when x=1,y=2.

If $x = 1$ ; $y = 2$ find the values of the following expressions :
(i) $4 x - 3 y + 5$
(ii) $x^{2} + y^{2}$
(iii) $x y + 3 y - 9$