Solve: x2 - 20x + 36 = 0
a: {6, -6}
b: {2, 18}
c: {-4, -9}
d: no solution

Question

Solve: x2 - 20x + 36 = 0
 a: {6, -6}
 b: {2, 18}
 c: {-4, -9}
 d: no solution

welshfella · Answer

you need 2 numbers a and b where a * b = +36 and a + b = -20

welshfella · Answer

these numbers go into the binomial
(x + a)(x + b) = 0
then solve for x

welshfella · Answer

this equation will factor

welshfella · Answer

think of the factors of +36

4 * 9
-4*-9
2 * 18
-2 * -18
3 * 12
-3*-12

are some of them

welshfella · Answer

- which of those give you -10 when added?

welshfella · Answer

* -20

anonymous · Answer

You have been given points in your options, you can put them in your original equation and check which one is satisfying that equation..

anonymous · Answer

$$Given\ eq: \ x^2-20x+36\ x^2-(18+2)x+36\ [ \because 36 \times1=36=18\times 2 |18+2=20]\x^2-18x-2x+36\x(x-18)-2(x-18)\(x-18)(x-2)\ \therefore\ original\ eq\ reduces\ as \ (x-18)(x-2)=0\ \implies \ either\ x-18=0\ or\  x-2=0 \ i.e.\ x=18 \ or\ x=2\hence\  (b) is \ correct \ option.$$