If 4x-3y=1 and 5x-7y=-2 then 3x+4y is

1.	If 4x-3y=1 and 5x-7y=-2 then 3x+4y is
Answer» Answer $\sf \dashrightarrow 4x - 3y = 1 \: \: --- (i)$ $\sf \dashrightarrow 5x - 7y = -2 \: \: --- (ii)$ By FIRST equation, $\sf \dashrightarrow 4x - 3y = 1$ $\sf \dashrightarrow 4x = 1 + 3y$ $\sf \dashrightarrow <klux>X</klux> = \dfrac{1 + 3y}{4}$ Now, let's FIND the VALUE of y by second equation. $\sf \dashrightarrow 5x - 7y = -2$ $\sf \dashrightarrow 5 \bigg( \dfrac{1 + 3y}{4} \bigg) - 7y = -2$ $\sf \dashrightarrow \dfrac{5 + 15y}{4} - 7y = -2$ $\sf \dashrightarrow \dfrac{5 + 15y - 28y}{4} = -2$ $\sf \dashrightarrow \dfrac{5 - 13y}{4} = -2$ $\sf \dashrightarrow 5 - 13y = -2 \times 4$ $\sf \dashrightarrow 5 - 13y = -8$ $\sf \dashrightarrow -13y = -8 - 5$ $\sf \dashrightarrow -13y = -13$ $\sf \dashrightarrow y = \dfrac{-13}{-13}$ $\sf \dashrightarrow y = 1$ Now, let's find the value of x by first equation. $\sf \dashrightarrow 4x - 3y = 1$ $\sf \dashrightarrow 4x - 3(1) = 1$ $\sf \dashrightarrow 4x - 3 = 1$ $\sf \dashrightarrow 4x = 1 + 3$ $\sf \dashrightarrow 4x = 4$ $\sf \dashrightarrow x = \dfrac{4}{4}$ $\sf \dashrightarrow x = 1$ Now, let's find the answer of this question. $\sf \dashrightarrow 3x + 4y$ $\sf \dashrightarrow 3(1) + 4(1)$ $\sf \dashrightarrow 3 + 4$ $\sf \dashrightarrow 7$ Hence, the value of 3x+4y is 7.

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