Question

I dont know how to solve equations by completing the square x^2 −51=14x

Answer 1

`x^2-51=14x\\\\\implies x^2-14x = 51\\\\\implies x^2 -2\cdot 7\cdot x+7^2-7^2 =51\\ \\\implies x^2 -2\cdot 7 \cdot x +7^2 = 51 +49\\\\\implies (x-7)^2=100\\\\\implies x-7 = \pm√(100)\\\\\implies x =\pm10+7\\ \\\text{Hence,}~ x=17, ~x=-3`

Answer 2

or, x^2-14x-51=0

or, x^2-(17-3)x-51=0

or, x^2-17x+3x-51=0

or, x(x-17)+3(x-17)=0

or, (x-17)(x+3)=0

Either, x-17=0. Or, x+3=0

x=17. x= -3

Hence,x=17, -3