`a)`
`(2x+5)(2x-7) - (2x+3)^2= 16`
`=> (4x^2 - 4x - 35) - (4x^2 + 12x + 9) = 16`
`=> 4x^2-4x-35-4x^2-12x-9=16`
`=> -16x - 44=16`
`=> -16x= 60`
`=> x=-15/4`
Vậy `x=-15/4`
`b)`
`(2x+3)^2 - 4 (x-1) = 49`
`=> 4x^2 + 12x + 9 - 4x + 4= 49`
`=> 4x^2 + 8x + 13 = 49`
`=> 4x^2 + 8x -36=0`
`=> x^2 + 2x - 9 =0`
`=> (x^2 + 2x+1)-10=0`
`=> (x+1)^2- (\sqrt{10})^2=0`
`=>(x+1-\sqrt{10})(x+1+\sqrt{10}) =0`
`=>x+1-\sqrt{10} =0` hoặc `x+1+\sqrt{10} =0`
`+)x+1-\sqrt{10} = 0`
`=> x = \sqrt{10} -1`
`+)x+1+\sqrt{10}=0`
`=>x=-\sqrt{10} -1`
Vậy `x \in {\sqrt{10} -1 ; - \sqrt{10} -1}`
`c)`
`49x^2 + 14x + 1 =0`
`=> (7x)^2 + 2 . 7x . 1 + 1^2=0`
`=> (7x+1)^2=0`
`=>7x+1=0`
`=>7x=-1`
`=>x=-1/7`
Vậy `x=-1/7`
`d)`
`16x^2- (4x-5)^2 =15`
`=> 16x^2 - (16x^2 - 40x+25) = 15`
`=> 16x^2 - 16x^2 + 40x - 25 = 15`
`=> 40x - 25 = 15`
`=>40x = 40`
`=>x=1`
Vậy `x=1`
`e)`
`(8x^2 +3)(8x^2-3) - (8x^2-1)^2 = 22`
`=> 64x^4 - 9 - (64x^4 - 16x^2 +1) = 22`
`=> 64x^4 - 9 - 64x^4 + 16x^2 - 1 = 22`
`=> 16x^2 - 10 = 22`
`=> 16x^2 = 32`
`=> x^2=2`
`=>x=+-\sqrt{2}`
Vậy `x \in{+-\sqrt{2}}`
