Question 17

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Jambmaths question: 

Find the value of x and y respectively if $3x-5y+5=0$and $4x-7y+8=0$ 

Option A: 

(–5, –4)

Option B: 

(–4, –5)

Option C: 

(4,5)

Option D: 

(4,5)

Jamb Maths Solution: 

$\begin{align}  & 3x-5y+5=0----(i) \\ & 4x-7y+8=0----(ii) \\ & \text{Multiply }(i)\text{ by }4\text{ } \\ & \text{Multiply }(ii)\text{ by }3 \\ & 12x-20y+20=0----(iii) \\ & 12x-21y+24=0----(iv) \\ & \text{Subtract (}iv\text{) from }(iii) \\ & y-4=0 \\ & y=4 \\ & \text{Substitute }4\text{ for }y\text{ in }(i) \\ & 3x-5(4)+5=0 \\ & 3x=15 \\ & x=5 \\\end{align}$

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