Mohon bantuanya nomor a dan d Plese

a).
[tex] {x }^{2} = {75}^{2} - {21}^{2} \\ {x}^{2} = 5625 - 441 \\ {x}^{2} = 5184 \\ x \: \: = \sqrt{5184} \\ x \: \: = 72[/tex]